On Wednesday, September 16, 2020 at 6:23:34 AM UTC-7, John DeRosa OHM Ω http://aviation.derosaweb.net wrote:
This seems to be the year of smart watches adding O2 sensors. Garmin has a whole line of them from $200 to $1200. How does the Apple watch do in direct sunlight as in our cockpits? As a trial I bought an inexpensive smart watch from BangGood which worked fine for reading O2 but was basically unreadable in sunlight.

I just got the Apple Watch 6 and have tried the O2 sensor a couple of times.. It reads within 1% of the fancy and expensive finger O2 sensor thingy.
Close enough. I have not checked its readability in sunlight. I'll do that tomorrow.