As I wrote before, this thread is for techies only.
This is For those who are interested in creating their own embedded computer project...
Can I get some Java with the Raspberry Pi?
I wrote a little Python script recently that recognizes hand gestures and also head positions - by this, I added a recognize “no” routine by movement of the head from left to right. It should run on on the Raspberry PI, but I haven’t had a chance to try it yet. Computer vision is rapidly progressing and OpenCV is a great little library to include in your Python install.