Funny, my wife is a sign language teacher and that’s actually one of the most appropriate uses I can think of at the moment. It’s a very complex problem, but there have already been a number of schools using the Kinect and similar devices to try and develop ASL translators which I think is pretty sweet considering how much work has gone into voice/text translation. It’s also a challenge since ASL has a lot of regional influence and also requires interaction with facial recognition since facial expressions are part of communicating.