Because if this really is that good, and that cheap, they've crossed a fundamental line. We're looking at a hardware accessory that has a good chance of being as ubiquitous, and maybe even as revolutionary, as the mouse.

Yeah, I'd be shocked if this replaces the scroll wheel. I can see a few ways it might complement existing input devices, though. One is for maybe a dozen intuitive, system-wide shortcuts. Like "if I stick out two fingers and twitch to the right within six inches of the screen, and I'm not in a touch-enabled app, switch to the next song." (This takes too long to say -- try doing it.) Or, "if I make the classic 'stop' hand gesture within six inches of the screen, stop playing music." This may not sound like much, but imagine a random non-geeky user is playing music in the background and gets a phone call and wants to pause. I bet 25% or less of users use a system-wide shortcut for that. I bet 75% or more would intuitively remember and use the "stop" gesture if you showed it to them once.

A second use case is collaboration. Someone comes into my office and I turn my screen around and show them a map of a given facility we're working on. (This happens a couple times a week.) They want to zoom out a little and see what's to the west of the facility. Instead of asking me to do that, they just reach in and do it with gestures. They don't think about it, it just works.

The third use case is all those things we do with our hands in real life that there's no analog for on the computer. Like, say, oil painting. Or conducting. Or playing rock-paper-scissors. Or air guitar. Or juggling. Or ping pong. There are a million things we do that involve holding something in the air and using it to cause some effect on the world, with little or no direct physical feedback. There are a million more that we haven't thought of yet because they're not physically possible (but they will be virtually possible).

I'm pretty excited about this.