Val, I agree with you about online courses! There are already video lessons out there, but this would be personalised.
Touch is usually easiest, but it's possible to teach solely by demonstration/explanation. I was thinking mainly of older/adult students who would be able to copy/listen. It's not quite the same as being there, of course. There are 2 features I need to consider, though:
1) the camera has a mirroring effect so if I show you writing, it comes out backwards.
2) the sound doesn't work simultaneously in both directions, apparently.
That said, other musicians are already doing it. I guess you just have to be a bit creative. It must be better than a video because the student gets immediate feedback.
I think I need some real-life English teaching practice, but tutoring kids/teens is more my thing for general subjects. Just no maths.