There are three basic categories of tutoring: homework help, "close the gap", and full course replacement. The first two are standard fare and no problem. However, in my field of chemistry, full course replacement requires lab work, and that is problematic for a couple of reasons. For safety reasons, labs can *only* be supervised in person; that difficulty can be overcome by enlisting a local tutor's assistance, facility, equipment, and supplies, which raises its own issues. Computer simulations exist, but I have not found them satisfactory. "Kitchen" labs are adequate for the simplest exercises.
For homework and lecture, I use a combination of video clips and live document camera (with a headset so the audio is as clear as the video) so the student can see and hear in real time what I'm explaining or working out. Seeing my *face* is of little value, but watching what I'm writing and/or calculating is extremely valuable. On the student's side, a document camera is also helpful (about $100 new), but we can make do with a webcam, scanner, and even good clear pictures from a cell phone camera.