Today you can do almost anything with a smart phone, except get out of the agreement you signed when you bought your smart phone. Now, use your beloved gadget as a frickin' robot controller, with Sphero.
Created in a faraway mountaintop lair ominously referred to as "Boulder", Sphero is an opaque, polycarbonite-shelled robotic ball packed with RGB lights and equipped with an accelerator and gyroscope that are controllable with remarkable accuracy via Bluetooth from an iPod/Pad/Droid, though really, this crazy ball is the droid you're looking for. The surprisingly not-too-expensive, semi-sentient orb can be guided by either swipes of the finger (when you'll intermittently power it with racing-ready speed boosts!) or swinging your device like a Wii-ldman, optimal for future-is-kind-of-stupid-yet-I'm-still-transfixed fun like Sphero mini golf. After you've hit another type of green, play even wackier games, like one where zombies appear in a phone-encapsulated video of your surroundings and you roll Sphero over them to kill them, or "Kittycam", where you tap your fingers on a pair of paw-prints in an attempt to outrun your cat, entertainment that, after Sphero, is pretty much the only reason your cat won't become obsolete.
They've also got an API that allows for the programming-minded to create their own games. The API is free, though to actually create addictive games you'll need to be as smart as your phone -- and look at you, you can't even get out of your contract!