New Scientist is reporting on new gaze tracking technology designed for use in 3D virtual worlds. Gaze tracking has been used for years by people with motor neurone disease, cerebral palsy and other "locked-in" syndromes, but only to operate desktop interfaces. This more recent technology will bring the likes of Second Life and World of Warcraft to people who can't play them with a keyboard and mouse.
According to the article, the magic is a suite of "eye gestures" that includes (among others, presumably) glancing off-screen in pre-defined directions. The gestures let the eyes become more expressive than they are when they're used simply as a mouse. This has obvious advantages for people with severe motor deficits.
Mainstream applications: In a car, your eyes could be used as a "dashboard mouse"--looking at any control would be equivalent to pressing it. Fan speed, station, current disc and track, brights, nav system--all could be adjusted with a quick glance and gesture. Dangerous? Depends on the dwell time. If you have to hold your gaze for a second, that's clearly unsafe. But if it were only a few milliseconds, you might be okay.
Another idea (not mine): A car that tracked its driver's gaze would know whether she was looking into the mirrors frequently enough and sound an alarm if not. This would clearly have a high impact (as it were) on safety, not to mention being teeth-grittingly annoying, which would tend to keep the driver alert.
And around the house? Remote controls, perpetually lost, encrusted with bean dip, and crippled by dead batteries, could be replaced with eye gestures. Operating the menu on your entertainment system would be straightforward (just use your eyes as a mouse) while eye gestures (circle, triangle, pentagram, looking from center to north, northeast, east, and so on) could control non-menu functions (volume, channel, etc.).
Today, a couch potato still needs to operate that remote, which keeps his right thumb fit and toned. Gaze tracking could make his potato-hood complete. Although he would, I suppose, develop muscular eyeballs, which probably counts for something.