How to Optimize Your Health with React Native

Kumar describes heart rate variability (HRV) as variation in the time between heartbeats and presents it as a signal of stress and recovery. His app compares recent HRV with a longer-term baseline to help users decide whether to take on work, keep to plan, or rest.

Kumar chose an iOS app because he needed access to HealthKit data, which a web app could not provide for this use case. He uses React Native to work with familiar JavaScript and TypeScript while accessing native features, and says it also makes sense when a team wants a mobile app without a separate web app.

The app presents four readiness states, from complete rest to going hard, using a traffic-light style interface. It compares a 60-day HRV baseline with a recent seven-day trend and also considers the coefficient of variation. Kumar demonstrated simulator data and added low HRV samples until the app recommended taking it easy.

Kumar chose Expo to manage React Native builds, upgrades, and deployment through Expo Application Services and TestFlight. He selected a HealthKit library by checking its recent commits, issue response times, and npm download trends. Because the app processes health data on the device, it works offline and does not need a separate database.