According to this article http://www.tomsguide.com/us/heart-rate-monitor,review-2885.html http://www.tomsguide.com/us/heart-rate-monitor,review-2885.h..., sever

According to this article http://www.tomsguide.com/us/heart-rate-monitor,review-2885.html http://www.tomsguide.com/us/heart-rate-monitor,review-2885.h..., several consumer products are accurate to within 1 beat of an EKG.