I had a strange idea come through my mind after seeing a Nissan commercial with the intelligent key..

Would it be possible to turn a standard Dell USB key into a car key? With modifications to the car, of course. I'm seriously thinking about the idea.. Think about the possibilities.. House keys, car keys, every kind of key wrapped into one shiny 512 USB key. Anyone have any thoughts on this one? Advice, tips, warnings, whatnot?