Really cool project, and thank you for writing it up so well! My first question is "why" and the post answers that well (my paraphrasing): because Apple Watch

Really cool project, and thank you for writing it up so well! My first question is "why" and the post answers that well (my paraphrasing): because Apple Watch is more accurate than anything else on the market, and health can be a matter of life and death. OP is definitely an open source guy though so even if you'll never buy another Apple product (like myself) it's still a fascinating look at the current state of things!