An idea for iOS 8
I've got an iPhone 5s and I have an idea for upcoming major update of iOS (Only for devices with Touch ID). When a person you know, i.e. my younger sister, takes the phone and touches the button, the fingerprint scanner automatically takes her to something like 'Kids Corner' in WP 8 (You have to register his/her fingerprint before and prohibit apps you want to).
Wouldn't that be cool?