Apple's watch doesn't have continuous, only on-demand HR, correct? I think they have better options and I would trust them much more than anybody else regarding choices of materials and so on. And, yeah, Basis doesn't have an API and that's another reason not to waste money into it. It's been years and they still keep our data for themselves! As a beta tester, I told them that I don't mind paying an annual fee to get access to an API, they told me they are working on it (2 years ago), and, yet, there's nothing to date!