Can the front camera be used to recognize finger movements in the air?

I've just seen a video of a mouse using a camera to recognize finger movements.
http://www.youtube.com/watch?v=_aFT8j8NcVk
(Other mice use proximity sensors.)

Can't the n900 do that also?
E.g as complement to touch screen (e.g.: You tap on a spot on the touch screen and then you do a mouvement in the air with your fingers?)