When iOS 6 becomes available for the masses it will be bringing along a new accessibility feature with it as introduced today at WWDC 2012.
Guided Access - as it is called, will allow users to selectively remove portions of a screen from use, disable hardware buttons or even disable certain portions of an app.
On stage, Apple shared the example of autistic children, with whom you may only want to allow certain functions of apps. Users will be able to effectively block out any settings you wouldn't want to allow access to, but the uses could go well beyond that. This feature will also be able to be open up new possibilities for users in stores, museums, in schools and even restaurants. It's a pretty awesome feature to have included and it will surely help a lot of folks out there.