Hello. I am a quadriplegic who uses voice control to control my iPhone. That's all well and good until I find myself in a loud room, or I find myself in a space where I can't speak freely. So I've been looking forward to eye tracking. I am sorely disappointed. I have my iPhone mounted firmly on my wheelchair, about 12 inches away. I find that it's tracking accuracy is very poor. Question — I can move my head a little. Should I be moving my head to change my focus or should I keep my head perfectly still and move only my eyes?