The NaturalPoint SmartNAV 3 allows you to control your computer cursor without using your hands — an obvious boon for those who suffer from debilitating pain or hampered mobility. Instead, you plug in the USB sensor, put it atop your monitor and attach a disposable dot to the center of your forehead, which allows the sensor to track your movements. Just swivel your head around and the cursor will follow suit. Clicking isn't so easy, unfortunately, though NaturalPoint offers a few different methods, such as a foot pedal.
The SmartNAV 3 units are offered in three flavors: the most basic allowing you to keep your mouse stationary (though you will still have to click), and the most advanced coming with a virtual keyboard and incorporating an alternative clicking method. The fact that the sensor won't operate unless you place a dot on your head and be able to move your neck assumes the user has quite a bit of mobility left, so we're guessing NaturalPoint isn't targeting the severely disabled, but rather offer relief for stressed wrists.
The good news: it's cheap. Depending on which version you go for, the SmartNAV 3 units cost from $225 to $400. Click through for a video.