I just saw a video for the “Mycestro”, pronounced somewhat like maestro, on IGN and it looks interesting. Basically, the device clings to your index finger and lets you use it as a pointer wand. Movement engages when the thumb touches the thumbpad, and it has three buttons below for click events (which apparently allows click and drag). Dragging your thumb against the thumbpad acts as scroll events.
Seeing the reporter, Alaina Yee, attempting to use it makes it look a bit more precise than a Wii remote, but a definite step down from a mouse or even a trackpad. It looks like it could be annoying, or at least take some practice, to use in a desktop environment, but a home theater PC with a “20-foot UI” might benefit from the convenience (if it can be taken on and off easily).
On the other hand, it has the capability of tracking in 3D space, despite its current role as a mouse. An SDK is not yet available, but the company says that it is in development. Of course, if future applications is what you are interested in, you may want to wait until after the development kit is released to see what it actually supports.
The Mycestro is available now (and has been since November) at their website for $149.