Laser can track movements in 3D space and in realtime.
Now, I don't have to tell all you geeks about what kind of doors this opens up for us gamers....this baby can track multiple objects (albeit at a slower speed) without needing an additional hardware setup, you could do WAAAY cooler things than what the Nintendo Wii's remote will let you do. Imagine a fantasy game where you are a wizard....instead of being limited to making gestures with a wand (with the Wii) to cast your spells, imagine being able to make complex hand gestures and have recognition software in the game that can determine how accurate your movements are and if you got the spell correctly it would cast it, and if it was close, there might be variations, it might fizzle, etc. Suddenly you can take a game like WoW that is all grind and hitting buttons at the appropriate intervals to a game that requires a LOT of skill to be a caster. Especially for higher level spells when you are in the middle of combat and speed and accuracy are essential.
I'm sure there are other applications beyond gaming, but for now all I can think of is making the coolest magic-based fantasy game ever!