Apple already has a number of health monitoring features on their Apple Watch and it looks like iOS 14 will bring some more including blood oxygen detection.
Health blood oxygen levels are between 95 percent and 100 percent, levels below 80 percent can led to health complications like cardiac arrest and others.
Apple is apparently developing a new blood oxygen detection feature for the Apple Watch which will be released with iOS 14, this was recently discovered by 9 to 5 Mac.
Apple will apparently be able to add this feature to existing versions of their smartwatch as it can use the same hardware in the device that Apple uses to monitor your heart rate.
Apple are expected to release iOS 14 later in the year along with their new iPhone 12 handsets, which were expected in September but could now launch in October.
Source 9 to 5 Mac