Very interesting: Surface tracks shapes with its vision system. There are five cameras in the Surface. The system has a very high resolution (dice can be tracked). Surface uses high-power leds with a mirror system.
via blogs.msdn.com
Pictures of the actual LED and the light scattering mechanism that Surface uses can be found here.
It seems like Surface uses Osram SFH 4740 high power LEDs. Available in Germany here.
Most of this information has been found in that thread in the nuigroup.
Thanks, Stu.