Naman Chauhan from SRM University created a proof-of-concept project that measures your resting heart rate and sends the data for analysis via a $5 Wi-Fi device. The project is fully documented with the source code on either Hackaday or Hackster.
Naman uses an Arduino for processing the heartbeat data and turns the data into heartbeats per minute. Then, periodically, the device sends the data to ThingSpeak for data storage and data analysis using MATLAB. The heart rate monitor is connected to the internet using DFROBOT’s ESP8266 Wi-Fi Bee. The Wi-Fi Bee turns serial data-to-Wi-Fi.
This heart rate monitor sensor is a pulse sensor which is developed based on PPG techniques. This is a simple and low-cost optical technique that can be used to detect blood volume changing in the microvascular bed of tissues. It is relatively easy to detect the pulsatile component of the cardiac cycle according to this theory.