Whoop Strap 3.0 ProKnit - Onyx WS30 The WHOOP Strap 3.0 collects physiological data 24/7 to provide the most accurate and granular understanding of your body. It's lightweight, waterproof, and features the new and improved 5-day battery life and BLE connect. WHOOP uses its sensors to detect changes in heart rate, the ambient temperature, and movement patterns. Every morning, get a detailed report telling how much time was spent in bed, how long it took to fall asleep, how long was spent in each stage of sleep, and how many times sleep was disturbed.