A rather convenient device to monitor heart rate while running.
Here I show you how an ESP32 can take ECG and send this data to cloud. And how to set up web app to look at this data.
If you want a device that could measure your heart beat and plot its curve trace on an OLED display, then this will be your best guide.
I used this example for save ECG signals in SD card. It was the adaptation of the SD card example from Arduino IDE.
This work the design and implementation of a digital system based on open hardware development board applied to heart rate estimation.