Check out this short video by Johnny Lee, a PhD student at Carnegie Mellon University. Using a Wii remote, a small LED array, and some reflective tape, he shows how you can have an interface which tracks the movement of your fingers.
Cool, huh? He talks about how the interface is similar to that used in Minority Report, though I was also thinking about the bit in Jurassic Park where the researchers manipulate virtual strands of DNA using their hands. Lee says that using your hands might not be practical because it's tiring. As the sole method of interacting with a computer, I'd think so. But as a peripheral to compliment existing means of interaction, or for certain special applications (e.g. computer-aided design), I think it would be extremely useful.
They should give this guy his PhD and someone should hire him so he can get this stuff to market.