It’s pretty common for people to hand off an iPhone or iPad to a child and let them play with it for a while.
The risk in that is you can somehow find your iTunes account has “accidentally” bought new apps and features that end up costing you hundreds of dollars.
But you can actually stop a child wandering around by locking the device to just one app in iOS 6. To do so, head to Settings, then open the “general” tab followed by “accessibility”. Then, under “guided access”, switch to “on”. You can lock whoever uses the device into an app – whichever app you choose.
You can show the device the areas you don’t want people touching, and set an unlock passcode for when you don’t need to use the feature anymore.