I already saw that "Face API", but I won´t be able to create something like that on my own, and they haven´t released it to the public yet.
This combined with a pair of 3D Glasses...
I had this idea too and will definatly give it a try
But with red/cyan glasses and not with shutterglasses.
this would be (in my mind) used if you were to make avertual reality game were the player were a sort of helmet or somthing of that nature which contained a screen so the players eyes never leaves the screen and a wirless keyboard/controler would be recomended if the player desides to do a 360 and look behind himself.
I would integrate a compass into that hardware instead of using a webcam :P