The app operates as a separate launcher and appears to be fully customizable. Parents (or guardians) can select individual apps, music and video that may be accessed by the kid they are about to hand the device to. It is accessed by swiping left from the lock screen and seems nearly as easy to leave as well, simply hit the power button.
Expect this feature to be available on all Windows Phone 8 devices.
source: The Verge via Engadget