High blood pressure is independently predictive of heart disease and stroke. We see this over and over again in prospective cohort and RCT data the same way we know that your favorite metrics also predict heart disease.

The problem with your wearables example is the same problem you have with angiograms and CAC scans: by the time you're seeing results, it's probably too late.

Even if the Apple Watch could tell you 7 days before you're going to have a heart attack, it's the result of decades of cumulative exposures to factors including hypertension that have lead to the plaque, stenosis, ventricle hypertrophy, and fibrosis that underly your heart attack.