Pretty good !

Hi, Ive used the app just a few times, but one of them was while flying a plane at 18,000 ft, while using supplemental oxygen to keep my levels up. It would be much more usable if it could read lower levels than just the 90s, but for the price its a nice general indicator which works as advertised.

goldilocks_dave about Pulse Oximeter - Heart Rate and Oxygen Monitor App, v2.2.0