Is there anyway to "lock" open a single app in iOS?

My use case for this is simple. There are many apps and games designed for children. While these applications are appropriate for children, many other applications installed on an iPad are not.

But even more so than protecting them from inappropriate content, I would just like to prevent them from leaving the application. They accidentally hit the home button or multi-touch gesture out of the application. I know you can turn gestures off. Developers also have links to their website or other related applications.

Kids are constantly exiting the application and then bringing the device to me asking "Can you get me back into the game?" every couple minutes.

How can I hand a child an iPad with "Angry Birds" running and make sure only "Angry Birds" runs?

Cydia or jailbreak tweaks welcome. Thanks.