Well, the R&D guys at SCEA went and did it. They’re using facial recognition to track on head on the screen, instead of using IR LEDs strapped to your head. They demonstrated it at GDC, cool stuff!
The feat was reported by Kotaku, Gizmodo, Joystiq and others, but essentially they all point to the same video on mtv.com which has a silly IP ban for UK, Japan and Canada. Those countries clearly have no right to know about glassless headtracking.
Same video on youtube with no IP ban: