This was envisioned in a science fiction story or novel decades ago, but I can’t remember where I saw it! It might have been a novel by Robert Heilein. It was j

This was envisioned in a science fiction story or novel decades ago, but I can’t remember where I saw it! It might have been a novel by Robert Heilein. It was just mentioned in passing in the story, but since that time I’ve wondered if it will ever be realized; I thought it might take the form of a small robot about the size of a June bug that would slowly crawl around in one’s mouth while we were asleep.