The scientist who tests those is Rob ter Horst: but as said previously, his accuracy tests are controversial: https://petergamma.org/category/is-this-product-part-of-a-marketing-trust-marketing-trusts-are-forbitten-in-switzerland The scientist who uses those for writing papers: Peter H Charlton: The 2023 wearable photoplethysmography roadmap: https://iopscience.iop.org/article/10.1088/1361-6579/acead2 together with around 50 co-authors: Peter H Charlton48,1,2, John Allen48,3,4, Raquel Bailón48,5,6, Stephanie Baker48,7, Joachim A Behar8, Fei Chen9, …