RFID Implant - Flickr photoset (See what I'm talking about)
Follow the link above for more images. This dude just decided to implant an RFID chip in his hand (think: proximity security badge at work), for home automation/automatic computer login/etc.

I'd be lying if I said I hadn't thought of this.. I've been trying to think of a killer use for RFID for a while now (so far: put an RFID chip in bikes to identify after stolen, ala dog/cat implants; again, RFID chip in bike(s), car(s), valuables so that you can be notified when they leave a certain area: "Your [bike/car/dildo/whatever] has left [bedroom/garage/freezer/etc]". Shoot - even integrate with home security system so that when X leaves Y, it kicks off a camera that can record exactly HOW X left Y.

As Fasana would say: "PATENT PENDING!"