I've tried to do position triangulation with RFID signal strength and had pretty terrible results. I suspect wifi would be just as bad. An infrared system would probably work well I think. (I know you addressed this)

That being said, sign me up. I have a friend with an oculus dev kit and it has blown me away time and time again. I can see this kind of thing becoming reality. Just stick foam padding all over the place and you're golden.