He wanted to do a little more with the equipment so he ditched the watch and built an Arduino-based heart rate monitor. He’s still using the chest strap and was happy to find that SparkFun sells ...

You may be interested in a project published to the Hackster.io website earlier this year providing instructions on how to create a simple wearable heart rate monitor using an Arduino Nano R3.

He managed to build his own monitor using an Arduino. The trick of this build has to do with how the system works. The panel includes an LED light that blinks 1000 times for each kWh of electricity.