Wristwatch Monitor

Best heart rate monitor for a child – help!??
For people out there FITNESS! I need your help. I no experience using a pulse or a monitor of human resources. I need something that my 7 year old son can use. I would like something he will not have to press a button to see its heartbeat. It would be nice to have something that beeps to alert you if the pace Heart goes a certain amount, a reminder of the watch as it becomes more anxious (need to use biofeedback). I looked at the type of wristwatch and want one like. Thank you – it's really important to us. My son is not a pawn in an evil sort of experience. He is autistic and he can not calm down! He learns visually, so if he can see his heart rate rising, it will help to calm himself. This is called biofeedback and it is a legitimate form of therapy. I am an educator and I need advice on buying the right type, no parental guidance.
The Polar F4 is a specific version of the women who should respond to a child. It has an alarm function. Certainly a seller to Dick / Sports Authority / Running Shop to get one of the packaging for your son to try it.
PARS Video