Assistive technology for the disabled is the higher use for mouth-input, but it'd be great to have a simple bluetooth mouthguard with media playback controls (play, pause, next previous) for action sports.
- Single tap on the roof of your mouth: play/pause.
- Tap on the inside of your upper left/right teeth: previous/next.
- Drag your tongue along the inside of your teeth: playback scroll.
- Drag your tongue on the roof of your mouth from front to back and back to front: volume up/down.
It seems very intuitive, and like it would be much more precise than any of the finger gestures we use today. My only concerns would be comfort, mistaken inputs, and impact on speech. But then again, some people wear dental jewelry and it doesn't seem so bad. :)
When I do a bike ride, for me, the silence is a feature.