I recently noticed that my fitness wearable (Whoop) started automatically estimating V02 Max and in talking with clients this week I learned Apple, Garmin and many other popular wearables do the same. I wrote about this health and fitness metric back in 2019. I’d say the results given by wearables are “cool” and “interesting”. If you want to get more precise, you can perform a more robust and more accurate test wearing a mask while performing strenuous cardio (usually on a treadmill but also possible on a bike or rower).