But these kids do things with phones that they think no one else can see. Have you ever read the EUL agreement on the apps that either are installed or that you put in. Everyone has complete control of the device. And they use these things for everything.
Pictures have code that identifies where you are at all times, GPS enabled or not. Every call, picture, email, text, is databased somewhere by someone for some reason.
If you don't want up close and personal prying eyes to see what you have on that device or what you are doing, don't have it out and accessible when with them. I have face recognition software on mine. My wife can't open it and see what's there. Not that I have anything to hide, she's welcome to it at any time.
The new laptop I just bought has fingerprint recognition software. Not to hide anything from her, but should it be stolen, unless that thief has geek knowledge about this stuff, the average Joe can't open your stuff.