Worth to note that is not just some obscure small company coming out of nowhere to capitalize from Apple. Masimo is a decades-old medical equipment company, with several developments and patents for non-invasive PPG. Apple is obviously well-aware of their developments, and was in touch with them already in 2013, more than a year before the launch of the Apple Watch.
From the actual lawsuit filed by Masimo in 2020 [1]:
"In 2013, Apple contacted Masimo and asked to meet regarding a potential collaboration. Apple told Masimo that Apple would like to understand more about Masimo’s technology to potentially integrate that technology into Apple’s products. Apple and Masimo later entered into a confidentiality agreement, and Masimo’s management met with Apple. The meetings included confidential discussions of Masimo’s technology. After what seemed to Masimo to have been productive meetings, Apple quickly began trying to hire Masimo employees, including engineers and key management."
[1] https://fingfx.thomsonreuters.com/gfx/legaldocs/byvrlojrdve/...