Measuring pulse is a tricky business due to the low amplitude of the signals involved which are usually only a few milli-volts. Photoplethysmogram (PPG) is a method of detecting pulse which works using an IR LED and an IR photo-detector. IR light is shone into the skin and the amount reflected back changes as the blood pulses through the body.
The signal from the photo-detector needs to be amplified before it can be effectively sampled by an Analog to Digital Converter like the ones found in most micro-controllers. This is where the Easy Pulse Plugin steps in to save the day. It uses the MCP6004 Quad Op Amp made by Microchip for amplification. From reading the documentation page, it’s clear that a lot of work has gone into the circuit design to get the cleanest possible signal out. The board is also Arduino compatible, designed to plug directly into an Arduino’s header pins. It can also be plugged into a breadboard for use with whatever microcontroller you work with.