The controller generates a kind of virtual-space bubble in front of your PC, one large enough to accommodate your two hands (though many apps require only one). Imagine a 10-point multitouch interface, like you'd find on a touchscreen, but in three-dimensional space. The sensors track not only the positions of your hands and fingers, but also their movements. Thus you're able to "interact" with onscreen objects without actually touching anything.
Let me just pause right here to note that any business user hoping for a Leap Motion-powered productivity edge will be disappointed. You cannot design industrial components a la Tony Stark in Iron Man, nor can you sift through virtual files like Tom Cruise in Minority Report. We are a long, long way from that.
Apps for air
The Leap Motion Controller runs on apps, and there's already a decent collection of them in the Airspace Store -- about 75 as of this writing. These run the gamut from games to drawing tools to music makers, with a smattering of productivity apps for good measure. Some are free, while others cost a couple of bucks. A few will seem familiar to anyone with a tablet or smartphone, including Cut the Rope and Google Earth.
I started with Cyber Science - Motion, which displays a photorealistic model of a human skull and lets you rotate it, zoom in and out and remove individual pieces -- all through a combination of hand and finger motions. It's really cool, and one could see where a student -- one studying anatomy, anyway -- might find this a helpful educational tool.
At a Glance
Leap MotionPrice: $79.99Pros: Compact, inexpensive, easy to set upCons: Little productivity value, it's challenging to use some apps effectively
Google Earth, on the other hand, proved an exercise in frustration. Unless you maneuver your hand with slow, exacting precision, the globe spins hopelessly out of control. That's because it responds to every single hand movement: toward the screen, away from the screen, up, down, tilted left, tilted right and so on. Without considerable practice, it's impossible to get where you want to go -- or even just take a simple flight across the mountains.