A quick and easy heart rate BPM monitor using HTML5 Audio
https://sean-bradley.github.io/BPMHeartRateMonitor/ (Best viewed using Google CHROME)
You should use an electronic stethoscope plugged into your pc to use this BPM heart monitor properly.
I have created a tutorial which shows you how to do this using cheap parts you can buy online.
Build a cheap electronic stethoscope
Enjoy