Probably not very many. Fun anecdote: When the Google Glass first came out I wanted to use it to record procedures so that we could create an annotated video dataset of medical procedures to see if we could match outcomes to actions. When I talked to medical professionals about it though they told me no Doctor would wear it for fear of malpractice lawsuits so it never really got off the ground. I guess you could go the opposite way and talk to the insurance companies about forcing surgeons to wear it but that didn’t sit well with me.