Korean-American entrepreneur. Co-founded Fitbit with Eric Friedman in 2007, pioneering consumer fitness wearables. IPO in 2015. Sold to Google for $2.1B in 2021. Departed Google Jan 2024. Feb 2026: launched Luffu, an AI-powered family health and caregiving platform inspired by caring for aging parents. Fitbit defined the wearable category that Xiaomi/Huami later dominated on price. Currently self-funding Luffu in limited beta.