In order to measure Blood oxygen levels you need a Red and an IR LED. Can you confirm that the watch has this? Just because its a plethysmograph doesn't mean it can measure oxygen levels. It needs the different wavelengths to determine the ratio of oxygenated hemoglobin, and non oxygenated. All I have ever seen is green LEDs, which are not capable of doing this. What makes you think its capable of being a Oximeter.