"Has anyone used both the Viatom/Wellue CheckMe O2 Max and the O2Ring?" I just been using the o2Ring for 6 months. I just received a second oximeter, the CheckMe max. I intend to use them side-by-side while I exercise, do normal activities, and sleep with cpap/supplemental o2. I need readings that ...

I've read that oximeters that are FDA 'Approved' require a Rx to purchase, and that o2Ring is FHA registered, and that It is not FDA Approved. https://www.fda.gov/medical-devices/safety-communications/pulse-oximeter-accuracy-and-limitations-fda-safety-communication https://www.fda.gov/medical-device...

Look at it this way:
With o2 disorders, a person is like an jet pilot occasionally dependent on supplemental oxygen to stay alive.
This person should insist on accurate, dependable, trusted equipment with double-system failure prevention . No matter the effort, cost, or inconvenience.