Apps supporting in-app at launch include Tap Tap Revenge by Disney Mobile, Comics by ComiXology, Gun Bros, Deer Hunter Challenge HD, and WSOP3 by Glu Mobile and Dungeon Defenders: FW Deluxe by Trendy Entertainment.

Google has also provided documentation, a complete sample app, and info on how to implement the service, set up in-app product lists, and test the implementation.

In addition, third-party mobile services company Urban Airship is working on a "last mile" tool that will make implementing Google's new system even easier for developers. Similar to the service available for iPhone, UA's beta for In-App Purchases on Android is now underway.

Features supported in the program include:

• Dynamic content: The Android Market limits application size to 25mb (even over Wi-Fi). Apps with rich content and media files can use UA's In-App Purchase offering to grow beyond that. Developers upload paid and free content to UA's servers and it delivers the content to the end user when needed.
• Security: Urban Airship reduces complexity around security by validating all purchase receipts before delivering content to the application.
• Versioning and updates: Urban Airship tracks updates to purchasable content and notifies users when updates are available. Developers can also fixes bugs in your updates without shipping an additional app update.

The sign-up form for this program is still live on UA's website here.