over the past 12 months or so I have done a half dozen comparisons while at the doctor taking a SpO2 reading and my AW was within 1% all the time, so I call that rather accurate ... still, it's not a medical tool as you saySorry but I have seen many people complain that the sensor is not very good. And it should NEVER be used as a reliable medical tool, only as a guide at best. Also I never said I do not see ‘usefulness’ of a the feature, that is you assuming things, also you are again assuming claiming I am in good health, how do you know?