Amazon.com: Concord Fingertip Pulse Oximeter with Lanyard …

The Concord digital fingertip pulse oximeter uses advanced technology to monitor SpO2 (blood oxygen) – and heart pulse rate (PR) via a large bright OLED display which allows you to read in the dark or bright light.It runs up to 30 hours on a single set of AAA batteries and shuts off automatically after eight seconds to avoid unnecessary draining.

https://www.amazon.com/Concord-Fingertip-Pulse-Oximeter-Lanyard/dp/B08925BSQJ