The In-app Billing on Android Market to developers and users is now launched. In-app Billing gives you more ways to monetize your apps with try-and-buy, virtual goods, upgrades, and other billing models.
As an Android developer, you will now be able to publish apps that use In-app Billing and your users can make purchases from within your apps. If you aren't yet familiar with In-app Billing, you can learn more about it.
Several apps launching today are already using the service, including 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.
To try In-app Billing in your apps, start with the detailed documentation and complete sample app provided, which show how to implement the service in your app, set up in-app product lists in Android Market, and test your implementation.
Also, it's absolutely essential that you review the security guidelines to make sure your billing implementation is secure.