I communicate exclusively with eye gaze. My progressive lenses didn't calibrate so well with the original tobii.
I love the tobii eye tracker hooked up to regular tablet. It calibrates well with my glasses,
I use Microsoftsurface,.
I practical practiced for a year before I had to use it,. I hated giving up my iPad but love my Microsoftsurface with tobii eyegaze attached.
also recently my children commented they were so glad I recorded my voice. The computer sounds much like my voice.
I have a set up like Vincent is describing attached to a Microsoftsurface and I love it, I found the Tobii slow and clunky. My only complaint is that it won't work with Apple products, unless that has changed recently