1. The gaming companies are already working on technology to follow player's motions without the markers. So in a few years I imagine you'll put on the sixthsense device, do a few hand exercises to calibrate it and that'll be all you need.
2. I still think he's focusing too much on video data displays. Audio through an ear piece is a lot more private and non-intrusive.
3. One interesting way to interact between the physical and virtual worlds would be to create a wiki tied to GPS co-ordinates so people can input information about any physical point on the planet. so, for example, your GPS/phone notes your location and can tell you the nearest coffee shop etc - and also bring up third party comments about the coffee shop.