What would be really cool, because just about everyone carries a cell phones now, is some kind of technology to integrate a cell phone into the body. Maybe a Bluetooth device, powered by some kind of fuel cell that could convert glucose and oxygen from the bloodstream into electricity.
Better yet, make the device a flexible, subcutaneous sheet, maybe made of silicone or something, incorporating a touch-sensitive array that would show through the skin when actuated, for example by selectively activating corresponding pixels tattooed onto the skin. Push a certain spot on your forearm and a cellphone display appears ... or, for that matter, any downloaded static or animated tattoo design.
You could even configure the circuitry to be able to monitor for blood disorders, and provide some kind of alert to the person if anything's out of whack.
Oh wait, it's been done.
(Gizmodo article here, thanks to allah_sulu for the story.)