From Raspberry Pi Tutorials:
Not only with fitness watches, but also with the Raspberry Pi it is possible to measure pulse / heart rates. With a small module – the Raspberry Pi pulse sensor – you can easily measure your own pulse and thus monitor permanently your health condition. This sensor can also be used in mobile Raspberry Pi applications (fitness tracker project? ;-)) thanks to low power consumption.
What is still needed and which libraries can be used are shown in this tutorial.
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