Dexcom Share — Homey App

A Homey app that follows one or more Dexcom Share CGM (continuous glucose monitor) accounts, bringing live glucose readings, trend, and alarms into your smart home.

Homey App Store listing: https://homey.app/a/com.dexcom.share/

⚠️ Not for medical use. This is an open-source, community-built project and is not supported by Dexcom or any other company. It is not officially approved or regulated for diabetes therapy and/or treatment in any way. Do not rely on it for medical decisions — always use your Dexcom receiver or official Dexcom app as your source of truth.

Living with diabetes, or caring for someone who does, means keeping a constant eye on glucose levels. This app brings the CGM data you already rely on into Homey, so a dashboard widget keeps the latest reading and trend in view at a glance, while Flow cards let your home react on its own when glucose runs high, drops too low, a trend is changing rapidly, or a sensor goes quiet.

Features

• Unlimited followers. Each paired device follows one Dexcom Share account — pair as many as you need (e.g. one per family member), with no cap.
• Live dashboard widget. A per-device widget shows the current reading, trend arrow, a severity badge, and a sparkline chart of recent history. Tap the chart to cycle between 3h, 6h, 12h, and 24h windows.
• Flow cards for triggers (glucose changed, high/low/urgent-low/rapid-change detected, no data detected), conditions (glucose above/below a threshold, trend is a given direction), and an action to force an immediate refresh.
• Per-device settings: mg/dL or mmol/L units, configurable urgent-low/low/high thresholds, and a no-data timeout — each account can be tuned independently.

Requirements

• A Homey Pro or Homey Self-Hosted Server.
• A Dexcom account with Share enabled, belonging to the person wearing the sensor (a separate Dexcom Follow-only login won't return data — see Pairing below).

Architecture overview

• app.ts — thin entry point. Holds no app-level shared state; its main job is broadcasting every paired device's already-polled snapshot to the dashboard widget (see below).
• drivers/follower/ — the follower driver/device pair. Each paired device owns its own DexcomPoller instance and its own unit/threshold settings; there is no shared service between devices.
• lib/dexcom/ — the core polling and domain logic, unit-tested independently of Homey. All communication with Dexcom's Share API goes through the third-party dexcom-share-client npm package:
  • DexcomPoller.ts — self-rearming polling loop (~5 min cadence, with backoff on errors) that fetches readings and history in a single call per tick.
  • glucoseAlarms.ts — derives a mutually-exclusive severity band (urgent-low/low/high/normal) and rapid-change flag from a reading, handling staleness and edge-only capability writes.
  • units.ts / thresholds.ts — mg/dL ↔ mmol/L conversion and the settings-form logic for resolving threshold values when units change.
  • timestamp.ts — corrects a timezone bug in dexcom-share-client's own date parsing.
  • client.ts — bridges the ESM-only dexcom-share-client package into this CommonJS app.
• widgets/glucose-dashboard/ — the dashboard widget. Binds to one followed device via a custom autocomplete setting (not Homey's native device picker — see the widget's own comments for why), and receives live updates over a shared realtime channel plus a polling fallback.
• test/ — node:test coverage for all the pure logic in lib/, plus the widget's own presentation logic (extracted and evaluated standalone) and a dev-only browser preview harness (test/widget-preview.html) for visually iterating on the widget without a real Homey device.

Pairing

Pairing uses a custom login screen (not Homey's stock template) that collects a Dexcom username, password, and region up front. The account entered must be the sensor-wearer's own Dexcom account (with Share enabled in their G6/G7/ONE/ONE+ app) — a separate account only used to follow someone else's data in Dexcom's own Follow app will sign in successfully but won't return any readings, since Dexcom's Share API only serves data to the account that owns the sensor session.

Development

npm run build          # tsc -> .homeybuild/
npm test                # tsc && node --test .homeybuild/test/*.test.js
npm run lint             # eslint, must be 0 problems
homey app validate --level verified   # the level CI runs at

See CLAUDE.md for a much more detailed architecture and decision log.

License

GPL-3.0