I have an ear thermometer (Braun) and a temporal IR (the kind that you actually touch to your forehead). We had both of these prior to the pandemic, I find that the temporal is good for daily checks but sometimes gives goofy readings. I usually run it 3 times in a row and take the average. The ear one is a bit more consistent.
The only other thing that I can think of would be a CPAP machine. Realistically one of these would only be valuable if hospitals are overrun and access to treatments is limited, so for most people will not be worth rushing out to buy one -- they are pretty expensive. But if I was high risk and if the current reopening starts to look bad I might consider it. Cautiously optimistic that this won't be necessary in the US.
Realistically our time and effort is probably better spent doing the things that are always good for us: eat right, exercise, sleep, get sun, use good hygiene practices, and eliminate stress. I hear that spending time in the shop and making pens is really good stress relief