Prey lets you keep track of your phone or laptop at all times, and will help you find it if it ever gets lost or stolen. It's lightweight, open source software, and free for anyone to use. And it just works.

"tracks what kind of software or games you use, and lets you create your own software profile." You can then share your profile for no good reason at all. This is very much a good, if limited, idea with 'social' tacked on.