What if you could pick out early warning signs of heart conditions just by looking at somebody and observing that they are overweight? It turns out that you can.
So, you're arguing that measuring other data points doesn't add value? Just look at someone and if they are overweight that's enough of a data point?
It's an empirical question. I would predict that you could do pretty darn well with height, weight, resting heart rate, blood pressure, bloodwork, and asking the patient about their physical activity. Fitness trackers are cool, but I'm just arguing against breathless health claims without justification.