It only became possible to do it in a wearable form factor very recently using a combination of the following 2 sensors: https://sensirion.com/products/catalog/

It only became possible to do it in a wearable form factor very recently using a combination of the following 2 sensors: https://sensirion.com/products/catalog/STCC4 https://sensirion.com/products/catalog/STCC4 https://www.bosch-sensortec.com/media/boschsensortec/downloads/product_flyer/bst-bmv080-fl000.pdf https://www.bosch-sensortec.com/media/boschsensortec/downloa... Not sure the market is big enough to invest my time.