iOS (a href="http://www.lifehacker.com.au/2011/05/how-to-jailbreak-your-ios-device">Jailbroken): While you can easily lock out content on your iPhone with a passcode, that doesn't really help when your friend wants to borrow your phone for a minute. FaBActivator is a jailbreak app that gives you precise control over what's available on your iPhone when you activate it.
FaBActivator uses an Activator action to trigger that lets you disable notifications, specific apps, Notification Center and multitasking. You can even set it up so people can't power down your phone or screw around with your volume settings. If you find yourself handing over your iPhone to people a lot, and you want precise control over what they can or can't do with it, FaBActivator is ideal. You can find FaBActivator in the Big Boss Repository on Cydia.