I bought this for my daughter, who is 6 years old and severely disabled. She frequently has issues keeping her oxygen level up and during those times it's nice to have a constant monitor on her. This oximeter reads the same as the finger clip style oximeter I bought at CVS, so I think it's probably pretty accurate.As for fit: they give you several little bands that can actually be velcroed together if needed. This will fit on pretty much anyone if you're determined enough, but definitely would work better for kids.