Boston-based health wearable company, Whoop, now operates in over 200 countries and grew revenue by more than 100% last year and is cash-flow positive. The company, founded by Will Ahmed in his senior year at Harvard, has sold itself as a secret weapon for athletes, with athletes such as LeBron James, Cristiano Ronaldo, Patrick Mahomes, and Rory McIlroy wearing Whoop's fitness band. The subscription model, which bundles hardware and software for between $200 and $360 a year, has proven successful. However, the FDA challenged this feature last summer, arguing that it constituted medical diagnosis rather than wellness monitoring. Other features include ECG monitoring and atrial fibrillation detection, which Ahmed says makes Whoop the first wearable to offer these features. The firm has also launched a blood testing partnership with Quest Diagnostics, which allows members to upload their biomarkers directly into the app, and a feature called Health Span calculates your biological age.