This courtesy of Metafilter--this chap apparently has subcutaneous RFID chips implanted in his hands with which he can log on to his computer and open doors. http://amal.net/rfid.html
This isn't too new technology, really. It's just that people are usually somewhat reluctant to put things like that under their skin, especially when carrying a card with chip works usually just as well.
It would probably be better to implant a chip such as this in ones wrist. The wrist is fairly mobile, but unlike the hand it does not grasp things and also does not have nearly as much tactile sensitivity.
For in that sleep of death what dreams may come
When we have shuffled off this mortal coil,
-Hamlet