I was pointed in the direction of this article by a colleague – a video of two people demonstrating a new system to operate Second Life using a webcam rather than a mouse or keyboard. The webcam picks up body movements and translates them into avatar movement, gestures and even expressions. Some of the movements are prescribed (hands behind back to land gracefully, for example), but many are natural: jump, your avatar jumps.
It’s only in the early stages of development, but it’s an interesting video nonetheless. But I am a bit disappointed you don’t need a spinning desk chair and a long corridor to fly any more…
That second link pretty much summarizes my experiences with my Second Life avatar so far!