The Geek Pub guide will help get you started with an Arduino pulse sensor. While sensors like this are reliable, it's worth keeping in mind that your heart rate can tell you a lot of different things.

[Sharathnaik]’s heart visualizer may not be all that electronically complex, but the execution is pulse-pounding ... finger on the heart rate sensor in the base, and an Arduino Nano actuates ...

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.

But now, with the rise of modular and kit electronics, you can build some of those devices right on your desk using a ...

Heart rate sensors available for DIY use employ photoplethysmography ... The refresh rate of the FT5x06 interface is adequate and the data is sent via an Arduino in 35-second chunks to the PC ...