Sparkfun page says the Polar Heart Rate Module – RMCM01, is out of stock and NOT available for backorder. There are comments from July 2011 asking about it but have not been answered Report comment ...

Internally his heart rate monitor is using an Arduino Pro Mini, a small OLED screen, and a turn-key pulse sensor which was originally conceived as a Kickstarter in 2011 by “World Famous ...

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.

Heart rate and oxygen sensor has LEDs and algorithms, ... The module consists of a MAX86141 dual-channel analogue front end chip plus a MAX32664C MCU and a pair of 3.8mm 2 PIN photodiodes. ... Arduino ...