I was going to write a tweak for iOS to do something like this, with behavior similar to that of the built in Camera shortcut from the lockscreen.<p>1. You are using an app<p>2. You activate 'Guest mode' using a button press, swipe, tap, etc. (configurable)<p>3. If the user hits the home button, it redirects to the lockscreen instead of the homescreen (much like the Camera application does in lock-mode)<p>4. Instead of the camera icon on the lockscreen when you double tap, it is the icon of the locked-in application. (You can tap it to resume use of the locked-in application)<p>5. To disable this guest mode, you simply unlock the device with your passcode.<p>So, when a friend asks "Hey can I check my email?", you can open Safari, enable this guest mode, and hand the phone to him, no worries.<p>What do you think?