Developer reverse-engineered WHOOP band and built an open-source app and backend to own your data

The WHOOP wearable band tracks health data around the clock — sleep, resting heart rate, heart rate variability, strain, and recovery — but the only way to access that data is through WHOOP's own app and a paid subscription. A developer spent several months figuring out how the band communicates over Bluetooth, then built a complete alternative stack: a phone app that pairs directly with the band and pulls data from it, a backend server that stores the data and calculates the key health metrics, and decoders for the band's communication protocol.

The project is split across four repositories (app, backend, analytics, protocol), all released under the MIT license. The backend can be self-hosted, meaning your data stays on infrastructure you control rather than a third-party service.

The goal is not to replace WHOOP's analytics — the company has years of research behind its algorithms — but to let existing band owners access their own data without a subscription. Currently tested only on WHOOP 4.0, and the user interface still has rough edges, but the system works end to end.