If you jailbreak your iPhone, there are quite a few things you can do that Apple may not have intended. One of those is enable Guest Mode. This is accomplished through a Cydia package called iPrivacy.
It’s a tweak that allows you adjust privacy settings and create a guest most, much like you may on a desktop computer. This means someone else can use your device without changing settings or checking your email, Facebook or photos.
Activating guest mode allows for them to set a different password and login. That way they can use whatever apps they want without disturbing your setup. It’s also useful for those who have children who like playing games on your iPhone. Give them a separate login, so they don’t mess with your stuff. According to Redmond Pie, the other user can respring, reboot power down, whatever they want. They won’t be able to access the things you lock out.
It’s a very cool tweak, and it runs for $1.99 you can pick it up on the BigBoss repository.