Developers can now incorporate contests and sweepstakes into iPhone apps, according to a new rule in Apple's SDK terms. The main restrictions are that a developer must be the sole sponsor of a promotion, and that an app comply with related laws. Apple also insists that the official rules for a promotion deny any sponsorship or responsibility on Apple's part.

In the past developers have only been able to show the results of contests such as lotteries. The new rule could, potentially, open the App Store to a number of titles with a gambling element. One such app has already been released, called KaChing Button. After paying for the app, buyers must push a button for chances at winning a $1,000 daily prize. The software has no other functionality.