Entrada analògica
https://github.com/lfwag/HeartSpeed
https://www.dfrobot.com/wiki/index.php/Heart_Rate_Monitor_Sensor_SKU:_SEN0213
20 €
Electrodes extra: http://tienda.bricogeek.com/home/1077-pack-de-electrodos-ecg-12-unidades.html?utm_campaign=newproducts-30-01-2018&utm_source=email