The Gaze-enhanced User Interface Design (GUIDe) project at Stanford has a nice video demonstration of their EyePoint system for "pointing" in GUIs (see below).
Eye-tracking technology has been around for a while, so that's not the interesting part. The interesting part is how they deal with the "Midas problem". The advantage of a mouse is that you can let go of the mouse when you don't want to move the pointer, but with eye-tracking your eyes are always moving. It's called the "Midas problem" in reference to the legend of King Midas, who wished for the power to turn things into gold at his touch; this backfired because everything he touched immediately turned into gold, including his food, his drink, and even his daughter.
EyePoint deals with this problem by still requiring some other action to indicate that pointing is desired, but without totally eliminating the speed of eye-tracking.