Measure the Oxygen in Your Blood
Granted, not every Apple Watch has this feature available, but the more modern models can measure and track your blood oxygen levels with a simple scan.
Your Apple Watch uses the light on its back to light your blood vessels. Based on the amount of light that bounces back, your Apple Watch can determine the oxygen level in your blood. It’s a pretty cool feature and works more accurately than people might think. Unfortunately, this feature is only available in the Apple Watch Series 6 and later models.