What kind of movement does a theft entail? Apple's in the process of figuring that out, today filing a patent application for a, "acceleration-based theft detection system for portable electronic devices." Apple pickers: you've just been put on watch. According to the patent filing, said device would activate an alarm of some form after determining, "whether a theft condition is present." It'll apparently figure that out based on the accelerometer built into many of Apple's mobile devices -- the same thing that figures out which way you're holding your phone. Beyond just the hardware, said theft protection system would work in concert with software to determine if the movement matches a pre-determined "profile characteristic of theft."
Of course, Apple's not the only one worried about mobile device theft, as Google already patented just such a device pertaining to its Project Glass concept. But the you'd have to be pretty brazen to steal the glasses off of someone's face without "accidentally" socking them in the eye.