Apple has patented a guest mode feature for the iPhone.
According to the description, the device owner will be able to restrict access to files and apps before handing the smartphone to other users. These users, in turn, will not be able to affect the owner’s data in any way.
The patent states that access can be granted to another user after they are authorized in some way. This is an additional security measure to ensure that not just anyone can use the guest mode.
The iPhone owner will always be able to change guest access settings from another of their devices.
Of course, this is just a patent, and there’s no guarantee that Apple will implement it. But it looks quite promising.