Open source programmed, uses a simple sensor that can attach to a simple pair of glasses or sunglasses, he built it himself while doing his senior year of high school, got accolades in fairs for it, and he’s selling it to support his way through college:

Honduran Teen Invents Cheap, Simple Eye-Tracking Device For Disabled:
http://www.popsci.com/diy/article/2011-11/honduran-teen-invents-cheap-simple-eye-tracking-device-disabled

At gizmag.com:
http://www.gizmag.com/luis-cruz-eyeboard-eye-tracking-computer-interface/20500/

You can invest here:
The Eyeboard – Low cost eye tracking system by Luis Cruz — Kickstarter:
http://www.kickstarter.com/projects/lcruz/the-eyeboard

I think this is the Do-It-Yourself kit for just $99.00:
http://www.intelsath.com/

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