Oh, Magilla Gorilla!,, this is just my opinion buuut... I'd pass on these. I've got one and yes,, it'll tell you your heart rate but they need to go back to the 'drawing board' with the design. You've got to hold onto the silver outer ring portion for the reading so anytime you bump it,, it wants to get the reading,,, uugh. There IS a lock function but the way you unlock it is to touch the screen and yea,,, you'll touch the screen naturally throughout the day. So mine sits around and works as a weird looking clock to remind me that I'm late :oP. I'm sure there are others that love this watch/monitor but for me,, it's a no-go.