Amazon.com: Innovo Deluxe iP900AP Fingertip Pulse Oximeter with Plethysmograph and Perfusion Index (Off-White with Black): Health & Personal Care
https://www.amazon.com/gp/product/B07YVGZPRZ/What’s a Pulse Oximeter, and Do I Really Need One at Home? - The New York Times
https://www.nytimes.com/2020/04/24/well/live/coronavirus-pulse-oximeter-oxygen.html