The pandemic has caused demand for oximeters to skyrocket (going from around £10 to £90 in some cases). I've been working on a project based on a the MAX30102 heart rate and oxygen level sensor which cost me only £5. Actually I am simply tweaking the code that someone else has written which you can see demoed here:

https://www.reddit.com/r/esp32/comments/g64w16/esp32_heartra...