Since you can apparently patent anything, they might as well patent the feature that the phone actually knows what your are thinking and performs accordingly.
Sounds like a nuisance feature. When I use my iPad, I look away plenty of times, but I wouldn't want it to lock up just because I looked away. It locks when I haven't used it for a particular amount of time, which is a settings that I can control.
A lot of these Android features tend to make a great demo, but not practical. That's the biggest problem with Android OS, some of their features add more code, require more resources and then cause battery drain.