Hi Justin,
First of all, great article! Lot a good info and resources to work on.
After my analysis on Fitbit sleep data, I am now working exactly on my heart-beat measurements, and your article provided me with many insight and ideas.
I will also have to dive deeper into the blood related biomarkers; as you pointed out they are harder to get, but definitely valuable!
Again, great post! Keep up with the amazing work!