I realize there are significant differences, but there would also appear to be similarities, especially in questions of safety, to cochlear implants. I have two and have written a popular book (Life After Deaf) about my experience, which includes having holes bored in my skull and a slim strand with 22 tiny transistors threaded deep into my cochleas. I got the first of these in 2010. No damage to date, or pain or side effects. I'm not a Musk fan, but his people seem to be on to something huge.