I've been very interested on this for a while. I even had the chance to work in a related project for a client for a very brief lapse of time (after a few years

I've been very interested on this for a while. I even had the chance to work in a related project for a client for a very brief lapse of time (after a few years working in games and virtual reality stuff). Most common solutions for this require real time computer vision, which is hard to develop, but very interesting of course...