This is measuring SpO2 or serum O2 isn't it? I've not looked to see what Garmin or any other is actually saying about for any devices they sell that have that feature. This thread was the first I'd heard of what I thought was a wrist worn sporting device.

I'm not sure that it'll show anything useful on a bike either. But who knows, it's something that does slightly peak my interest. But with only a SpO2 range of 95 to 100% saturation being generally considered healthy and anything 93% or less time for thinking about going on O2 or even a respirator I'm skeptical.

Even in my comment about muscle cramps and muscle fatigue I'm doubtful that it'll show anything. I think that is more how fast the muscles can rid themselves of CO2 localized around those specific muscle and not so much a function of the overall saturation levels of all the blood in our system.

I do think it's good for SpO2 to be monitored for overall health if it can be done reasonably. It might alert someone that the nagging cough and congestion in their lungs is a little more serious than just a common cold. I've got one of those pulse oxymeters that clip on a finger tip and it amuses me sometimes to see when it shows low SpO2 as opposed to when I think it should be low. Though that's rare. Usually I'm 98% or better.