I just received a Leap Motion controller and I am really impressed. You could think of this device as a 3D mouse or a sort of a short range Microsoft Kinect. And unlike so many gadgets that sound cool but when you get them fail to actually be exciting, the Leap Motion controller is even cooler than I hoped it would be.
The device is a tiny box (3.125" by 1.3" by 0.5") with a power-on LED that connects via USB to your OS X or Windows system. Plug the controller in, install the correct driver, and you have the ability to move the cursor by simply pointing at the screen (multiple monitors are also supported).
What is so impressive about the technology in the Leap Motion controller is that it can detect all ten fingers simultaneously to an accuracy of 1/100 of a millimeter in x, y, and z at a rate of 200 frames per second and discern gestures such as pinching.
This is a screenshot from Leap Motion's Orientation utility showing its analysis of where my hands were in the space above the controller. Note that all ten fingers are simultaneously detected.
You can download and launch apps designed to work with the Leap Motion from the company's Airspace Store. In the store there's a handful of free apps that demonstrate very effectively how the controller can be used as well as rather more that are priced from $0.99 (such as AirHarp, a harp that can be played by waving your hands) to $99.99 (AeroMIDI which allows you to control and play midi connected software and hardware).
While you can drive your computer using the Leap Motion controller its real value lies in applications that take advantage of 3D input. And the fact that you can relatively simply build support for the controller into applications and even Web pages makes the Leap Motion one of the most impressive gadgets I've seen for a while. And at a price of $79.99 it's a lot of tech for the money. Highly recommended.