iOS 6: Guided Access, Also for Kids and Kiosks
Guided Access is a new feature in iOS 6 that makes it easier for users with vision, hearing, learning, and mobility disabilities to use their iOS devices. The feature allows parents or teachers to limit an iOS device by disabling the physical buttons or limiting user controls on certain areas of the screen.
This could also be useful for parents with younger children who want to prevent them from leaving a particular app or game. Insanely Great Mac has put together a nice video showing how the feature works.