The R&D team at MS Research has demonstrated a prototype keyboard which, in addition to allowing you to type normally, is able to track your hands for gesture support.
The system uses a series of infrared sensors placed between the keys allows for what Microsoft refers to as "course, but high frame-rate motion data". Basically, the resolution of the data is quite low, but is captured at 300hz, giving the keyboard a good way of tracking your hand.
The keyboard is thin and compact, and from the video the extra hardware involved doesn't seem to have had much of an impact on the design at all. It looks a little like a slightly larger version of Microsoft's own Wedge Keyboard.
In many ways, this seems like a more sensible version of the Leap Motion controller, which was a good idea, but not brilliantly executed. Here, Microsoft seems to have limited itself to a set of gestures that are much like those you might use with a trackpad. But, the keyboard can detect both moving gestures, like pinch-to-zoom and static ones, where making an O with your thumb and forefinger, resting above the keyboard, starts a search.
Microsoft even says that it can isolate enough information to track your fingertip accurately enough that the keyboard knows what you are typing.
For now, it seems like the hardware needs to have the IR sensors exposed, and on the surface of the keyboard, which makes for a less than optimal typing experience. Presumably, in the future the sensors could be hidden within the keys themselves. When this sort of thing happens, gesture controls will certainly take off.
