Researching for our startup company, we looked around what recommerce websites are available already and what features they provide. This list is intended to be: a market overview for (aspiring) remanufacturers; and for consumers, an overview on how to sell comfortably and instantly on the Internet.

The list was last updated 2012-09-08 and is by no means exhausting. New recommerce companies emerge every few days. So if you know one not in the list, welcome to add it in the comments. (And, sorry for the lack of pretty formatting: this is an unchanged data dump from our own information collection “List of Buy-In Websites”.)

Want to create an own remanufacturing business? Here is a software for that.Mintybox logo small 2012-09-10 If you want to have a website for buying used electronics and media from consumers, similar to those below, you might want to look at our Mintybox recommerce software. It’s a startup where I am personally involved since 2009-08. So far we’re serving the German market, but welcome to drop us a line if you are from an international location. We will try to find a solution for your requirements!

Recommerce sites in order of country, then in alphanumeric order.


  1. – The Australian branch of the UK based remanufacturer They buy disused mobile phones.
  2. – They buy used and broken mobile phones, giving them a second life in developing nations.


  1. – An Austrian remanufacturer with an innovative collaboration with local T-Mobile shop dealers for trade-in.
  2. – A German remanufacturer who also allows to send in stuff from Austria with the provided shipment labels [source]. As of 2012-09, they buy 20 different kinds of consumer electronics and media.
  3. – They buy media, games and Lego (!).
  4. – Austrian branch of German Zonzoo.


  1. – They used to accept online trade-ins via their website “like anybody else”, but now have moved to partnering with the Fido retail shop network to accept trade-ins there.


  1. – Buy-in page of the mobile network operator Cofidis mobile. Powered with software of the of the white-label recommerce solutions provider, and running through their remanufacturing processes.
  2. – Buying used phones online with instant quotes, like others.
  3. – Cash for used phones, with instant quotes.
  4. – Site not working as of 2012-09.
  5. – The own buy-in site of the white-label recommerce solutions provider. It’s part of the solidarity economy, by employing socially challenged people in remanufacturing and by donating from the sales revenue.
  6. invendus por – An electronics buy-in site for members of PriceMinister only. Login required. Powered with software from the white-label recommerce solutions provider, and running through their remanufacturing processes.
  7. – Buy-in page of the mobile network operator NRJ Mobile. Powered with software of the of the white-label recommerce solutions provider, and running through their remanufacturing processes.
  8. – The new, second buy-in site of the white-label recommerce solutions provider. Launched 2012-03.
  9. – Buying many consumer electronics items, with online instant quotes.
  10. – Buy-in page of the mobile network operator Bouyges Telecom. Powered with software of the of the white-label recommerce solutions provider, and running through their remanufacturing processes.
  11. – Buy-in page of the mobile network operator Afone Mobile. Powered with software of the of the white-label recommerce solutions provider, and running through their remanufacturing processes.
  12. – Buy-in page of the mobile network operator Virgin Mobile. Powered with software of the of the white-label recommerce solutions provider, and running through their remanufacturing processes.
  13. – Funny site, buying disused phones for cash via their website.


Note: There’s also a German version of this part.

  1. – A relatively small / low-effort site, buying media and video games.
  2. – A German site that appears as if a small business is cloning
  3. – As of 2012-09, they buy 20 different kinds of consumer electronics and media.
  4. Amazon Trade-In – Amazon offers trade-in for used books since 2011-08-16, in collaboration with a third-party company [source].
  5. – A site buying used books, with some inspirations for ours.
  6. – Not functional as of 2012-09-08.
  7. – They buy DVDs, CDs and video games.
  8. – They buy media, video games and board games.
  9. – A book-only buy-in site.
  10. – They buy media (books, DVDs, CDs, BluRay). They sell via their Amazon shop and also state that openly on their site.
  11. – They buy books, CDs, DVDs, video games and gaming consoles.
  12. – They bought 90k books from 2008-09 to 2012-09.
  13. – A book buy-in site of one bookshop (Buchhandlung Oliver Barz). Small but nice.
  14. – They buy books. Data entry by ISBN, and they also offer to lend barcode readers for even faster data entry of large amounts.
  15. – Site that buys just only books online, since 2008-03.
  16. – A site buying audio and video media, playstations and games.
  17. – You can sell and donate a used phone here. Operated by ProPhone Solutions B.V..
  18. – A chain of three used-media stores in Ruhrgebiet, since ca. 1987. They buy right in their store, and have a guy travelling all over Germany to buy larger collections of media, all for ca. 20-30% of their new price or below.
  19. – Buys CDs. Broken as of 2012-09.
  20. – They buy all kinds of wearable electronics devices, and also software and computers.
  21. – They buy CDs, DVDs and video games.
  22. – They buy all kinds of electronics, but the offers are made manually on request.
  23. eBay Sofort-Verkauf – A cooperation of Flip4New with eBay, in analogy to eBay Instant Sale in the U.S.. The program started in Germany on 2011-07-28 [source].
  24. – They buy CDs, DVDs, BluRays, books, video games and gaming consoles.
  25. – They buy used phones. Dysfunctional as of 2012-09-08.
  26. – Registered as “SpyLive Entertainment & Security Devices Ltd.” in Cardiff, UK, but no UK branches were found. So probably just used for the legal form before the advent of German “UG haftungsbeschränkt”.
  27. – A trade-in operator, offering also actual trade-ins for exchange into new articles or coupons. They have an eBay shop to sell.
  28. – Buying media and video games. Looking good.
  29. – Webshop for used software, also having a simple form to buy in software.
  30. – They buy media, video games and phones.
  31. – They buy media, video games, consumer electronics and games.
  32. – Probably a media buy-in site. Broken (white screen) as of 2012-09.
  33. – A site buying gold, offering an inspiring “ready to go shipment set”.
  34. – A buy-in site for mobile phones, powered by equilibrium GmbH since 2009.
  35. – Buys all media and video games.
  36. – Buys books, CDs, DVDs and video games.
  37. – Claims to have bought ~900k books as of 2012-09 already.
  38. – A site buying video games, movies and audio media, with an inspiring process.
  39. – They buy media and video games.
  40. – This is us (just starting up)! That is, our buy-in portal for several merchants. We provide the trade-in software, but do not buy in items ourselves.
  41. – And still with test data in it, not finished as of 2012-09. However, claims they have them in their comparison already [source].
  42. – A buy-in site for seven brands of mobile phones.
  43. – A site buying used CDs, DVDs and video games. What’s interesting is that they do the price calculation by requesting prices in real-time from other websites. They are really big and well known. Among other things, they have smartphone apps to be used as barcode scanners for selling to them.
  44. – They buy defective notebooks, but not with an immediate offer.
  45. – A smartphone webshop that offers phone trade-ins as a special, at
  46. – A site that buys and sells on the same site; but only movies, books and iPods. Big and well-known.
  47. – They buy 6 million mobile phones yearly.
  48. – They buy video games, DVDs and BluRays.
  49. – They buy and sell CDs, DVDs, BluRays and video games, on the same site. They also offer iPhone and Android apps for the buy-in.
  50. – They buy video games, DVDs, CDs. Not a small site!
  51. – Specialized on buying used software licences.
  52. – A company buying via eBay from us and others, and selling successfully for even more.
  53. – They buy DVDs, BluRay discs and video games.
  54. – They buy books, CDs, DVDs and BluRays. Located in Limburg/Lahn.
  55. – They buy all CDs and also all vinyl / gramophone records, with and without bar code.
  56. – They buy all kinds of consumer electronics.
  57. – Buys caming consoles, movies and audio CDs.
  58. – A very professional and dynamic German trade-in startup, also known previously as
  59. – They buy CDs, DVDs and BluRay online and have a brick-and-mortar shop to sell them. And they provide an iPhone and Android app for selling to them, using the smartphone as a barcode reader.
  60. – A larger German based, but internationally operating buy-in business for mobile phones. Partially, they sell them to third world countries. They are probably the first company in the German electronics recommerce market.
  61. – They buy mobile phones, video game equipment and media.


  1. – A multinational site, doing buy-in and sale on the same page, even in the same offers. is their Irish branch.


  1. – A multinational site, doing buy-in and sale on the same page, even in the same offers. is their Spanish branch.


  1. – They buy all kinds of media and electronics, and also video games and other software.

United Kingdom

  12. – They claim to have paid out 100 million GBP already.
  33. – A multinational site, doing buy-in and sale on the same page, even in the same offers. is their UK branch.

United States

  1. Amazon Trade-in program – They state, “Trade-in items are purchased by a third party merchant.”. It is not clear so far if this is always the same, or if Amazon acts as a “remanufacturing tool provider” like we want to do with Mintybox.
  2. – Buy-back programs for the main categories of electronic devices, like PDAs, mobile phones, digital cameras.
  3. – Buying disused mobile phones. Broken as of 2012-09-08.
  4. – They collect mobile phones in collaboration with schools and non-profit organizations, for fund-raising purposes only.
  5. – Around since 2005, buying all the mobile phones.
  6. eBay Instant Sale – eBay does however not offer this feature itself, but in combination with one eBay reseller named AllTechWholeSale. This is shown for every selected item, so it seems eBay does not act as a portal currently, so is no competitor for Mintybox.
  7. – One can dispose old and unwanted electronics at their locations in California (nothing outside that as of 2012-03). Their website is optimized for mobile devices only, for some reason.
  8. – Company in California buying empty inkjet and laser cartridges, and alternatively, letting users support charity with their donations of waste.
  9. – A very large and high-quality buy-in site that collected 5 million in venture capital for their endeavour. They’re website is based on RubyOnRails (I once got the Rails failure box =). They sell also via an eBay store.
  10. – Buying used cellphones for cash via their website.
  11. – A California based company, founded 2011, offering to buy and else recycle the most common electronic gadgets.
  12. – MyBoneYard is a U.S. based company buying the main categories of consumer electronics.
  13. – Buying consumer electronics, movies and video games via their site. They seem to be around since 2005 already.
  14. – Buying used cellphones. In contrast to basically all the others, you just pack and send in the phones, without the need to register them online before. Prices are provided as PDF lists to look through.
  15. – Buying phones, iPods, iPads and games online.
  16. – Buying all kinds of mobile phones. They mail an envelope to send it in.
  17. – They offer a “guaranteed buy-back” program that can be bundled with new electronics, stating that people will get 50% for up to 6 month old devices, down to 20% for 2 years old devices. Around since 2005.
  18. – California based company doing desktop phone system repair and refurbishment since 1987, also buying used phone equipment via their site.
  19. – A multinational site, doing buy-in and sale on the same page, even in the same offers. is their US branch.
  20. – Around since 2009, buying all popular consumer electronics.

Special: Cars

  1. – Broken as of 2012-09-08.
  2. – AutoTrader is actually a network of many car dealers, and the trade in is also managed by several trading centers which do the final inspection before buying the car.
  3. – Auto Buyer is buying cash at ones home or office for cash, in California, Texas and Florida. 30+ years in the business.
  4. – Cash for Cars, having bought 50k cars since 1980 in the U.S..
  5. – They promise to collect the car from all locations in the U.S..


Welche Software eignet sich, um eine Ankauf-Website zu betreiben? (Auch genannt: Ankauf-Webshop, Ankaufs-Portal, Ankaufseite, Recommerce-Website, Buy-in Website usw. – es gibt noch keinen allgemein akzeptierten Namen.) Eine solche Website ermöglicht es einem Händler, ungenutzte Waren von Privatpersonen und Firmen anzukaufen, die er dann nach Aufbereitung und Reparatur wieder veräußern kann. In der Praxis sind das zumeist gebrauchte, aber gut erhaltene Medien- und Elektronikartikel, die in privaten Haushalten nicht mehr benötigt werden.

Es gibt ja bereits eine größere Zahl dieser Ankauf-Webshops – siehe die Liste von Ankauf-Webshops in Deutschland und international. Gute Beispiele in Deutschland sind etwa und Eine solche Website selbst zu starten war aber bisher schwierig, da nahezu alle existierenden unabhängigen Ankauf-Websites mit selbst programmierter Spezialsoftware betrieben werden. Damit war der eCommerce-Einstieg für kleine Unternehmen und Selbständige hier deutlich schwieriger als etwa mit einem eBay-Shop.


(Full Disclosure: Die hier vorgestellte Lösung ist das Produkt unseres eigenen Startup-Unternehmens, das wir seit dem 1.9.2012 anbieten.)

Mintybox bietet ein webbasiertes Programm für einen eigenen Ankauf-Webshop. Das Produkt ist eine SaaS-Lösung (Software as a Service): es muss also keine Software selbst auf einem Webserver installiert und gepflegt werden, sondern der Ankäufer erhält einen Zugang zu der existierenden Software. Also ähnlich wie bei einem eCommerce-Portal wie bei eBay, nur dass es hier um Ankauf statt Verkauf geht und dass der Ankäufer die Software mit eigener Domain ( verwenden kann. Das SaaS-Modell heißt aber auch, dass monatliche Gebühren (Verkaufsprovision und Grundgebühr) anfallen statt dass die Software mit einer Einmalzahlung »gekauft« wird.

Mintybox logo small 2012-09-10

Der obige Link zum Mintybox-Angebot enthält detaillierte Funktionsbeschreibungen und verweist auch auf die Mintybox Demo-Version zum Testen (Zugang: / demo). Hier aber noch ein paar Hintergrund-Infos, was potentielle Ankäufer zum aktuellen Zeitpunkt (2012-09) erwarten können und was noch nicht:

  • Praxiserprobt und in der Praxis entwickelt. Wir haben diese Software bzw. eine frühere Version davon unter dem Namen und später selbst für ca. 1,5 Jahre als Remanufacturer eingesetzt, d.h. wir haben gebrauchte Handys, Digitalkameras, Navis und Tablets gekauft, aufbereitet und gehandelt. Wir haben dabei in die Software alle wichtigen Funktionen eingebaut, die wir praktisch benötigt haben.
  • Produktkatalog: brauchbar, aber wächst noch. Der Katalog hat aktuell 2128 Elektronik-Produktmodelle mit Preisen (Stand 2012-09-07) und ein paar tausend mehr, für die noch Preise ermittelt werden und von denen täglich ein paar dazukommen. Das ist noch deutlich ausbaufähig, aber die wichtigen Modelle sind drin und die Software-Infrastruktur ist fertig – der Katalogausbau kann also zügig vorangehen.
  • Bücher: kommen als nächstes. Der nächste Schritt in der Softwareentwicklung ist die Produktkategorie »Bücher«, die zuerst alle deutschen Bücher mit ISBN enthalten wird – wir arbeiten gerade daran. (Datenquelle ist der Katalog der Deutschen Nationalbibliothek, genialerweise seit 2 Monaten unter CC0 »Public Domain Dedication« verfügbar.)
  • Anspruchsvolle Funktionen. Es sind bereits mehr als die absolutes Grundfunktionen eingebaut, unter anderem schon: Unterstützung zur Klärung von Abweichungen von der Beschreibung durch den Verkäufer, umfangreiche Konfiguration for Produktpalette und Preise, ein Bewertungssystem und die Integration mit der gemeinsamen Recommerce-Plattform für alle Ankäufer.
  • »Wir sind beta.« Die Mintybox-Software ist aktuell in der Beta-Testphase. Soll heißen, echter Einsatz ist bereits möglich und wird auch funktionieren, die ersten Ankäufer sollten jedoch bereit sein, sich bei auftretenden Fehlern und Unregelmäßigkeiten etwas in Geduld zu üben und die Probleme zusammen mit dem Mintybox-Team anzugehen. Dafür gibt es eine brandneue Software für ein bisher schwierig lösbares Problem. Die Unregelmäßigkeiten können auch noch die Genauigkeit der zur Verfügung gestellten Preise betreffen – mit dem Ankauf sollte man also vorsichtig beginnen und ein paar Erfahrungen mit einer »sicheren« Gewinnspanne sammeln bevor man diese wettbewerbsorientierter gestaltet.

Mintybox richtet sich an Gewerbetreibende, aber auch an solche, die es werden wollen: wer für die erste Ankauf-Website erst den Gewerbeschein beantragt, ist ebenfalls sehr gern gesehen. Unsere Idee bei Mintybox ist ein Netzwerk vieler »kleiner« Remanufacturer, jede(r) mit eigener Identität und Spezialisierung.

This happened to me in Magento when importing a single change to a set of products. That is, I had only two columns in the CSV file to import: teh sku column, and the column with the value to change. Now unfortunately I had a syntax error in this second column, so it got ignored. And the remainig sku column with zero other values seemed to tell Magento that I want all values removed. Which it did. The products disappeared completely from the catalog after that import.

Interestingly, they were not really deleted, “just” invisible everywhere. Because when I re-imported them wth the same SKUs they had before, every product got the database ID it had before, except one that I had completely deleted manually, which got a new database ID. (The database ID is the ID column in “Catalog -> Manage Products …” in Magento.)

I did not test the above theory with another case, as I was unnerved enough with the first (causing nearly data loss). If you can confirm this, please add a comment. Thanks 🙂

Invalid value for ‘status’ in row …

The correct values for the “status” field when importing form CSV files are:

  • 1 for “Enabled”
  • 2 for “Disabled”

This applies at least when importing via “System -> Import / Export -> Import”, maybe not to the Dataflow profiles (which, at least in earlier versions, used i18n’ed values like “Aktiviert” and “Deaktiviert” for German).

You can always check what values are the correct ones by exporting one enabled and one disabled product. Admittedly “1” and “2” instead of “1” and “0” is really counter-intuitive.

Invalid value for ‘generate_meta’ in row …

Invalid value for ‘imported’ in row …

This can happen when the locale you used for writing the file is differentf rom the interface locale setting when importing it. Check the “Interface Locale:” dropdown at the bottom of every page in the Magento backend for that! For example, the correct values for “generate_meta” when importing with German locale are “Ja” and “Nein”, but with English locale probably “Yes” and “No”.

When working with a Rails console to run some scripts on a database or similar, the default output of all the database queries and command results can be quite a lot and can slow down the processing considerably. Not to mention that it also can severely limit the readability of what your script outputs … .

Here is a solution, at least almost complete:

  1. Disable Rails 3.1 SQL logging (temporarily at least)
  2. Make the irb return value output to be always “nil”.

The by far best and simple variant is to download Buildroid 4.0.4 RC1.1 version 2012-06-10 with Google Apps and Houdini. It's a virtual appliance to be imported right into VirtualBox. The announcement for this can be found in BuilDroid: Running ARM apps, and there are some third-party installation instructions. As a special feature, this variant also includes the ARM-code to x86  translation via the houdini libraries, making it possible to run native / NDK apps on x86 even though they contain binary ARM code without the x86 equivalent. It might be that the graphics of this houdini variant are slower than without houdini; if you need the speed, try the variant without houdini (see its announcement).

It is also possible (in principle) to use a stock Android-x86 ISO image (I tried the 4.0.4 RC2 variant for eeePC) and install from that to a virtual hard disk in VirtualBox (somewhat outdated instructions, more of these but with good tips). However one has to fix several issues manually then which are already done in the VirtualBox-optimized BuilDroid build: getting the Internet connection to work (basically ifconfig, route, setprop commands on Android's console; see here in section Networking), plus getting the Wifi connection to work because else, logging in to Google Play is impossible (fixed in BuilDroid using a second, virtual network device).

Buildroid with houdini indeed can execute the NDK ARM apps (for example, Angrybirds, Facebook, Adobe Reader), for which the Google Play Market showed "your device isn't compatibel with this version" in other versions of Buildroid. However, some apps still show this message in Google Play Market, for a reason unknown to me so far. Among them, WhatsApp (version 2.8.1504) and MiTalk Messenger (version 3.1.435). It is possible to download their apk packages from somewhere with the browser and install them in Buildroid 4.0.4 RC1.1 houdini anyway (after allowing installation form non-market sources in the settings), but for example the MiTalk application apk will not work past the login screen. I suppose this is beause the BuilDroid image used here is built for tablets without phone capabilities (like sending an SMS, which MiTalk might want to do for verification). For other versions, there were also Buildroid images for phones and tabletphones, so another test could be made once such a thing with houdini becomes available.

Usage hints:

  • The VirtualBox mouse pointer integration does not work – your mouse will not work at all when it's enabled. So disable it in the VirtualBox appliance window with "Machine -> Disable mouse pointer integration".
  • It can happen that the mouse does not work to unlock the lock screen. In that case, press the "Windows context menu" key on your keyboard first. This should make the lock symbol emit some waves, showing it registered a keyboard event. And then the mouse is usable again.
  • When using the stock Android-x86 ISO images, I found that the mouse initially did not work on the start screen. Saving the VM state and starting the VM again at its saved state solved that issue, as per some tip from the Net.
  • Using the console in Buildroid is not as simple as in Android-x86 yet (where it's just pressing Alt-F1). There are instructions, but I did not try them.
  • When some Android app changes the screen resolution in VirtualBox (like MiTalk does), it's simplest to restart the virtual machine. The change is not permanent.


List of the requirements I have in mind. By importance:

  • available for Android.
  • no airtime minute use. This application must rely on data transfer only, especially to not cause any additional costs in usage across national borders.
  • wi-fi and mobile data connection options. The application must be able to use mobile data (whatever is available: GPRS / EDGE / 3G / HSDPA / LTE) to be usable everywhere, but also must be able to use wi-fi, to reduce costs and mobile data consumption when possible.
  • reliable delivery. That means, without voice loss and stuttering, even with difficult and intermittent network coverage. This implies automatic re-transmission until a voice message is successfully transmitted.
  • record-and-send mode. This mode is sufficient for semi-synchronous communication in instant messenger style, and more synchronicity is only needed in time-critical uses like on construction sites, festivals etc.. Record-and-send mode makes it possible to have reliable communication and intact messages even with difficult and intermittent network coverage. If there's an optional real-time transmission mode, this is a plus but not needed.
  • fast delivery. This implies automatic voice codec switching to adapt to low-bandwidth situations and intermittent network coverage.
  • optionally using the internal speaker for playback. This is a good idea to protect the sender's privacy when listening to messages in crowded spaces.
  • free and open source software. Very important, but not indispensable if there is really no free solution for this.
  • content encryption during transmission. Important, but not indispensable.
  • text messaging integration. Great to have when one cannot talk for privacy reasons or because of being in a silent environment.
  • desktop interoperability. It would be great to not be tied to the phone when working at the PC. But, this is optional. Apps which are not available as browser or desktop versions can normally be run on a PC in a VirtualBox VM using Android-x86 [instructions] or alternatively can be used from within your browser using the Manymo Android emulator. Manymo allows to install your own apps here, but be aware that you need to get APK packages for them first, you can't directly install from Google Play. Also, an emulator will go to suspend mode after 10 minutes of inactivity, so it's not a really great solution.
  • XMPP compatible. I'm using XMPP as my standard chat protocol now (and it is the official standard!), and it would be nice if the PTT application could integrate with this.
  • photo and video messaging integration. Optional, just nice to have.
  • gratis. If it can't be free, we want it at least gratis, right? 🙂


This list contains, to my knowledge, all apps with PTT functionality that were available as of 2012-07-15 (additions welcome!).

Tested and recommended: (starting with the most recommendable one according to my subjective evaluation)

  1. MiTalk Messenger. (Version of 3.1.435, 7.95 MiB) Really nice, as chat allows not just text and voice with its PTT button, but also "rich emoticons, photos, voice, location share, handwriting and graffiti, and more". Esp. the handwriting and drawing modes seem to be expressive and playful options. Also great, according to my tests: its tidy interface, gives feedback about message reception, notifies when the own Internet connection gets lost, notifications about messages received while offline (either as push notifications when enabled, or else when starting the app again and not being right in the chat to which the message belongs), quick transmission of voice messages, blue point icon for new messages in the thread, mode for using the earphone rather than loudspeaker for PTT messages, option to delete messages individually, and messages will only play at once if the screen is not locked and else cause a configurable message notification. The drawbacks, in this version: gratis but not free; the non-Chinese language versions are not in perfect shape; it's a Chinese manufacturer and they store the messages for (at least) forwarding them and there's no word about encryption and a rather lax policy about handing out your personal data, so better do not use it for any kind of sensitive data; the e-mail notification feature does not recognize that the notification is done; on older phones / Android versions (like the one of HTC Magic), the background mode does not work, so you will only appear as online when the application is shown in the foreground (seems because this uses push notifications, as mentioned in the config section, which might not be available in older Android versions. Also, one cannot send video (yet). And, when trying to install this version on Buildroid 4.0.4 RC1.1 with houdini, I failed to get it working; it should be tried again later [background].
  2. Zello Walkie Talkie. Clear and simple interface. No ads. It tries to automatically re-connect when network connectivity becomes available again. Includes an offline voice message history.  And, there's also a iPhone, Blackberry and PC client software. The flaws in the 2012-07-14 version: not free and open; sometimes loses messages and parts of it (this can probably be fixed by using the TCP config option instead of UDP); the only way to prohibit it from playing the messages aloud immediately is setting yourself to "not available"; missed message counter is always "1" even if there are more; and there's no way to reliably determine what the last unheard message is without hearing it.

Tested and not recommended as of 2012-07-21:

  1. WhatsApp. (Version 2.8.1504, 6.4 MiB) Allows to communicate with "messages, pictures, audio notes, and video messages". That's nice and it works well, but it's no true PTT app: it needs 6 or more clicks to send a voice message, which is handled like an attachment, rather than sending it with one touch-hold-release click in PTT style. Gratis for the first year, then 0.99 USD per year (though that is reportedly not enforced). Installation note: It might seem to be stuck with an "Initializing …" screen after choosing a screen name, but it just takes long to look for existing WhatsApp users if your addressbook is large (for example, 10 min for 900 contacts).
  2. KakaoTalk. Includes integrated voice and text messaging, both one-on-one and in groups. This is very similar to LINE, see there. In contrast to LINE, voice message transmission is reasonably fast. However, it needs five clicks and some waiting time to send each single voice message, compared to one click (hold and release) for most PTT messengers. Also, has no mode to use the handset's earphone instead of the loudspeaker. For these reasons, not recommended. Also comes with a teenie-style emoticon set and an in-app store for more emoticons, which could be considered a nuisance.
  3. Palringo. Allows voice and text messaging, and seemingly also to users of other services like XMPP [source]. It is however more centered around pre-existing chat groups rather than on one-on-one communication.
  4. pttdroid. The great thing is, it is open source. However, it's a very simple app and specialized on multicast and broadcast transmission in WLAN / LAN networks. It claims that one-on-one connections are possible via 3G, but I could not find how.
  5. LINE. (vesion 2.5.3, 11.4 MiB) Includes a chat with a PTT button (select "+ -> Audio Message" to get it) and also the option to send text, video and photo messages in the same chat. Look and feel and features are so much the same that this and KakaoTalk can be considered clones. Gratis but not free. It even comes with a desktop client, but that works only for Windows and OS X [source] but there's also a browser version that might (!) be usable on Linux and of course you can run it in a virtual machine like VirtualBox under Linux. Also includes SIP VoIP calls. See the manufacturer websiteTest results: In my tests, the app behaved quite sluggish, taking 15-20 s to transmit a 4 s audio message (from stop of recording to start of playback). Maybe a codec issue? In any way, this seems inapt for dialogue-style talking. Also, the emoticon set is quite … Asian, so not everybody's style.
  6. Virtual Walkie Talkie. Not tested.
  7. smart talkie (beta). Not tested.
  8. HipVoice. This is XMPP compatible, which is great [source]. However it's meant for business customers, which means that pricing starts at 10 USD monthly [source].
  9. mumble-android. Not tested. The start of a Mumble client for Android. This would be very cool to have, as Mumble is open source, comes with exceptional voice quality and voice encryption by default. However neither this particular software nor its forks are currently in active development because of some technical hurdles [source]. Also, while Mumble has a "push to talk" feature, it is not clear to me so far if its audio reception is not rather full-time on. That however would be too much for mobile data rates.
  10. Mangler. Not tested. A Ventrilo 3.x client for Android and thus a good replacement for the yet non-functional Android Mumble client. This client is open source, which is great, however the Ventrilo server is closed source (though gratis in a limited-capacity version). Mangler has PTT functionality [source], but as an audiospace type software, audio arrives as a continuous stream and not as messages. So, not usable in this context. And there is also Ventriloid, another open source Ventrilo client for Android that is based on Mangler.

Remaining to be tested:

  1. HeyTell. This is a freemium app. In widespread use and often recommended.
  2. TalkBox. Voice and text messaging. Also included photo sharing, conversation history, group chat and sharing to social networks.
  3. WeChat. Provides voice and text chat with multimedia elements. Frequently used application, Chinese manufacturer … .
  4. imo instant messenger. A gratis (though not open source) multi-protocol instant messenger, so interoperable with desktop applications. Though it is not clear if and how that also includes its voice instant messages. Also integrates group messaging, text messaging, video and photo sharing.
  5. TT Talk. The application integrates voice and text messaging seamlessly.
  6. Android Walkie-Talkie. This is one of the rare open source PTT apps, but not in development since 2009.
  7. VoxNotes Push To Talk. There is a commercial service behind, but that might be only to purchase credits for sending voice messages to any normal phone.
  8. coco voice. Comes with also integrated text and image messaging and optional posting to Facebook and Twitter.
  9. Blip. SMS style voice messaging, which is good because messages do not play immediately like in some of the other applications. Quite clear interface. Offline users will receive their message as an e-mail attachment. It has to be checked still if this style of interface is great for dialog-style communication, or rather just for occasional messages.
  10. GO SMS Pro. A SMS application, but also integrating PTT style voice messaging and text chat using data rates.
  11. pushFone.
  12. Voicely. Includes voice and text messaging.
  14. FreePP. Multimedia chat application including a PTT button, emoticons, photo sharing etc.. Might be a bloated app as per user reports, but that has to be checked.
  15. Walkie Talkie PTT Lite. Includes a message history for replay, and also allows to send voice messages to a group [source]. There are instructions how the data transfer of this app can be encrypted by using IMAP/S. This version has ads, the pro version has not.

Could not be tested so far:

  1. digisocial. The start of a very nice PTT application, but still in beta as of 2012-08-10. Because of its beta state, it had some bugs that made playing messages impossible on the phone used for testing. But When it finally starts to work and can be tested for real, it might easily get a recommendation here. It includes, among other things: sending text, smilies, images from the gallery, camera images, location information and of course voice messages; playback selectable via speaker or earset.
  2. Voxer. (Version from 2012-07-13, 2.3 MiB) In widespread use and often recommended. One of the most compact apps in this list. Needs at least Android 2.2, so not usable for some older phones like the HTC Magic and for that reason not tested here so far. Includes one-on-one and group messaging, as text, PTT voice message, photo message and location sharing.
  3. TiKL Touch Talk Walkie Talkie. Seems to be the most widespread PTT app on Android. It normally registers users by their mobile number so that one does not have to create an account. That however failed as my SIM did not contain that number, leaving me only with the fallback option of logging in via Facebook. And that's no option. What actually is this Facebook?