Believe it or not, when I was looking for a midi foot controller (I never bought one in the end) at the synthzone site dedicated to different websites for midi controllers, I ran accross one site that made midi controllers controllable by brainwaves. I never checked out the site, thinking that if it were that great of an invention, I would know about it. But Uncle Dave is right, thought controlled midi controllers aren't far off.
As far as voice control, humor aside, I don't think it's practical, because a musician doesn't want to announce what style or sound he wants - even if you turned off your microphone, it wouldn't be quite professional.
An optional computer touch screen that plugs in front of the music stand, now that would be really cool. The keyboard could have a fake book database on the hard drive, and you could see the lyrics in large print.
Larry