As consumer wearables track everything from our heartbeats to nightly sleep cycles, a new industry has emerged—one focused on making sense of this avalanche of personal health data. In an era when prevention is prized over cure, questions abound: How accurate is the data captured on our wrists and fingers? Can these metrics truly guide us to longer, healthier lives, or are we just generating noise? For Marco Benitez, a biomedical engineer and co-founder of the health data platform Rook,...