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 ...

Here's a good one, showing you how to build a heart rate monitor using a Genuino 101 with Bluetooth comms. The project takes advantage of the Bluetooth Smart comms (aka Bluetooth Low-energy) built ...

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.