There's now a Demo of the faceAPI tracking tool. It works great with my laptop web cam if the light is right.

They have also released a non commercial API now!

faceAPI

I'm not much of a programmer anything apart from some lite-C, so I have no idea how hard it would be to get this working with 3DGS. From what I could understand about the specifications somebody, like Slin :), could wright a wrapper for this and everybody could use it in their projects.

This tool could be used to determine the distance, angle and rotation of the player to the screen and open up a lot of interaction possibilities!