During quarantine, people with means have turned to obsessive health tracking as a hobby. Fitness tech startups raised a record $2.3B in 2020, per CB Insights, and connected fitness raised nearly $900M. As people learn more about their bodies, they're letting the apps make lifestyle choices for them. When Adeline Cheng wakes up, she checks the app on her phone that's synced with the chunky titanium Oura ring she wears to bed. While she slept, the ring measured her breathing, heart rate, body temperature, sleep quality, and movement. The Oura app displays her "readiness" score, meant to indicate how prepared her body is for activity that day. Combined with her "sleep" score and her "activity" score, Cheng is hoping for what's called a triple crown, meaning all three scores are above 85. Sometimes she gets it, she said.