There are also devices that connect with your energy source (how much energy does your house use per second etc.), with your curtains (automatically close or open them), IP camera's, motion detectors, door/window open/close detectors and much much more
But let's start with the basic stuff.
It happened to me quite a long time ago with an unknown phone (black&qhite screen, huh? I mean long time ago) with the train. I still remember my horror 

