As a teacher (not of tennis), a coach (not of tennis), and a parent; I find teaching devices interesting. This thread led me on a 15 minute search and the results are........
It is the same thing as THE EYE COACH! Sintherius, you are RIGHT!
If you need more proof, click on the link in this article for the HAL.
I guess you could also just go to http://www.haltennis.com