@Oliver1655 I think most of the pulse oximeters available on the market are pretty similar. Pick up one or two and start using them now, while healthy, to get a baseline. The main issues people seem to run into are nail polish and nail diseases throwing errors or strange readings. If the pulse registers strong, they're all pretty similar from what I can tell. I grabbed one from Walgreens a year and a half ago for like $30 and it has worked fine.