How to use the Blood Oxygen app on Apple Watch – Apple Support (UK)
Measure blood oxygen levels on Apple Watch - Apple Support
Apple Watch blood oxygen detection feature found in iOS 14 code snippet - 9to5Mac
O2 - Get six months free data on the Apple Watch Series 7 and experience the largest, most advanced, Always-on Retina display yet. Use the advanced features to measure your blood oxygen
The Paramedic's Guide to Blood Oxygen and the Apple Watch Series 6 - TidBITS
Apple Watch Series 7 Review: Is the New Wearable Worth Buying?