Tobii are giving Eyex (eye trackers) in their webpage, you have many chances to get one for free and also it's very cheap.
I was wondering if someone already had donde an eye tracking plugin for this or any other one, as far as i could see, Tobii have Unity, C++, .Net and Unreal SDK's but not for javascript.
you can see more of this in their webpage:
http://developer.tobii.com/downloads/