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RawPulse

RawPulse

Built: July 24, 2026

[ GitHub ↗ ]

WHOOP's own app shows recovery, strain, and sleep, but no live per-second heart rate. RawPulse fills that one gap: a home-screen widget that updates roughly once a second, plus a live HRV reading WHOOP doesn't surface at all.

It works by subscribing to the standard Bluetooth Heart Rate broadcast (0x180D / 0x2A37) that a WHOOP 4.0/5.0 emits when HR Broadcast is enabled, the same signal Peloton, Zwift, and Garmin read. Nothing goes through WHOOP's servers, there's no login, and there's no per-user setup.

Why not the WHOOP API

The official WHOOP Developer API is cycle-based (recovery, strain, sleep) and doesn't expose continuous heart rate at all. Per-second HR only exists locally, over Bluetooth, via the band's standard Heart Rate Service. WhoopHrManager subscribes to that stream directly instead of going anywhere near the cloud API.

Widgets

Four square home-screen tiles, all live while streaming is on:

  • Live Heart Rate: big BPM number, colour-coded by zone
  • Live HRV: rolling RMSSD over the last ~60s, not shown live anywhere in WHOOP's own app
  • HR Session: min / avg / max BPM and elapsed streaming time
  • HR Zone: percent of max HR with a zone-coloured bar

Architecture

Android's built-in widget refresh has a 30-minute floor, so real per-second updates have to be pushed, not pulled. A foreground service holds the BLE connection and pushes each new reading straight to the widgets, backed by a persistent notification with a Stop button. HrRepository is the shared source of truth that the service and every widget read from.

Trade-offs that come with that design: only one device can receive the WHOOP's broadcast at a time (so RawPulse and, say, Zwift can't both listen simultaneously), a persistent BLE connection costs noticeably more battery than idle, and losing range just freezes the widgets at their last value until the band reconnects.

Distribution

No Play Store listing: releases ship as signed APKs tracked through Obtainium, so installs update in place without needing to uninstall first. Zero-setup was a deliberate constraint: no WHOOP developer credentials, no per-user OAuth, just Bluetooth.

Stack

  • Kotlin, native Android, minSdk 31
  • BLE Heart Rate Service (0x180D): no cloud API, no login
  • Foreground service + AppWidgetProviders for the four live tiles
  • Signed release builds distributed via GitHub Releases + Obtainium