Ear-clip Heart Rate Sensor
sensoricon
port: Grove: A1 (C16, C17)
interface: digital
output values

1/0, high/low

Further information: https://calliope.cc/en/examples/heart-rate-sensor
Order: https://www.exp-tech.de/module/seeed-grove-system/4728/seeed-studio-grove-ohrclip-herzfrequenz-sensor

The Grove Ear-clip Heart Rate Sensor, is an ear-clip with an accompanying receiver, which can be used to measure the pulse.