Google announced the launch of Android Market In-App Billing for developers and users. Developers can publish apps that utilize it, and users can make purchases within the apps.

“In-app Billing gives you more ways to monetize your apps with try-and-buy, virtual goods, upgrades, and other billing models,” says Eric Chu, Android Developer Ecosystem.

The Android Market handles checkout details, meaning users won’t have to trust the apps themselves to process any financial transactions. It takes advantage of the same checkout process that the market itself uses.

Tap Tap Revenge, Comics, Gun Bros, Deer Hunter Challenge HD, and WSOP3, and Dungeon Defenders: FW Deluxe are among the apps already using in-app billing.

Google provides detailed documentation about in-app billing here, as well as a sample app and a means of testing an implementation.

There is a 30% transaction fee for in-app purchases.