Accurately determine your SpO2 (blood oxygen saturation levels), pulse rate and pulse strength in 10 seconds and display it conveniently on a large digital LED display.
This device has a 4.7 out of 5 stars rating on Amazon but note there are many others also to choose from. It is ideal for those who do not want to upgrade to more expensive fitness trackers that do SpO2. Measurements on the finger (like the Oura Ring) are said to be more accurate than on the wrist. Low SpO2 could indicate respiratory problems such as symptoms of Covid-19 or asthma. Note though this is not a medical device.
See https://www.amazon.com/Zacurate-Fingertip-Oximeter-Saturation-Batteries/dp/B07PQ8WTC4/