Most people have no idea why they feel great one day and terrible the next, and no fitness tracker that counts steps and flashes a heart rate is going to tell them. WHOOP doesn't count steps. It doesn't have a screen. What it does is monitor your heart rate, HRV, blood oxygen, skin temperature, respiratory rate and stress continuously, 24 hours a day, and turn that data into three numbers that actually matter: how recovered you are, how much strain you can handle, and how much sleep you need tonight. Used by LeBron James, Michael Phelps and professional sports teams worldwide because it answers the question every serious athlete and health-conscious person asks every morning: am I ready to push today, or am I running on borrowed energy? The 5.0 adds Healthspan tracking with a Pace of Ageing metric that quantifies your physiological age and shows whether your daily habits are accelerating or slowing the ageing process. 14+ days battery life, waterproof to 10 metres, wireless charging that works while you wear it so you never lose a minute of data. Includes a 12-month WHOOP Peak membership, SuperKnit band and wireless PowerPack.