I've had a couple different SPO2 meters for a few years, they seem to work pretty reliably.
Not yet as accessible as a thermometer if you're talking about population measures, but since it sounds like this is something that concerns you personally it might be worth getting one.
Unsure why I haven't hear anyone recommend those before, but that sounds like a good idea to get if one get infected. They are a bit expensive however so I am unsure if I personally want to pay that without a positive covid test.
a lot of people have undiagnosed sleep apnea or sub-clinical sleep breathing problems that can be improved by changing their position-- a logging spo2 meter that you can wear while sleeping can be a justifiable investment on that basis.
I've had a couple different SPO2 meters for a few years, they seem to work pretty reliably.
Not yet as accessible as a thermometer if you're talking about population measures, but since it sounds like this is something that concerns you personally it might be worth getting one.