A little side project: periodically sync my heart rate from Apple Health to a server and plot it in Grafana. It looks roughly like this:
Click the ♥️ in the top-right corner of the blog to view it. It runs through Cloudflare Tunnel, so access from China is slow; use a circumvention proxy 🪜 if possible. Now offline: after switching to an OPPO smartphone, I can no longer sync and upload heart-rate data.
The idea is to use the REST API feature in Health Auto Export - JSON+CSV to send heart-rate data on a schedule to a deployed HTTP endpoint. That writes it to InfluxDB, and Grafana connects to InfluxDB to draw the dashboard.
Scheduled syncing in Health Auto Export - JSON+CSV requires Premium. A lifetime license costs USD 24.99 in the US store—a little steep, but I could not find a comparable cheaper alternative.
After subscribing, create an Automation:
- Set Automation Type to
REST API. - For URL, enter the address of the service deployed below. The API path is
/push/heart_rate. - Set Data Type to
Health Metrics. - Under Select Health Metrics, check
Heart Rate. - Set Export Format to JSON.
- Sync Cadence can be one or five minutes. Apple Watch does not measure heart rate continuously.
Check Enable. Add a home-screen widget to help keep syncing after the app is closed.
Next, deploy the service, exposing a REST API endpoint that receives data and writes it to InfluxDB. I will leave InfluxDB installation to Google; note that the service uses InfluxDB 2.
The source is at reekystive/healthkit-collector. It is a Node project that can run directly with pnpm, listening on port 3000. I wrote a Dockerfile to package it as a Docker image and deployed it on my home server.
FROM node:20-alpine AS builder
# Install pnpm
RUN corepack enable && corepack prepare pnpm@9.14.2 --activate
# Set working directory
WORKDIR /app
# Copy package.json and pnpm-lock.yaml
COPY package.json pnpm-lock.yaml* ./
# Install dependencies
RUN pnpm install --frozen-lockfile
# Copy source code
COPY . .
# Build the application
RUN pnpm build
# Stage 2: Production stage
FROM node:20-alpine AS production
# Install pnpm
RUN corepack enable && corepack prepare pnpm@9.14.2 --activate
# Set working directory
WORKDIR /app
# Copy package.json and pnpm-lock.yaml
COPY package.json pnpm-lock.yaml* ./
# Install production dependencies only
RUN pnpm install --prod --frozen-lockfile
# Copy built application from builder stage
COPY --from=builder /app/dist ./dist
# Set environment variables
# These are default values that can be overridden when running the container
ENV NODE_ENV=production
ENV PORT=3000
# Expose the port your app runs on (using the PORT environment variable)
EXPOSE ${PORT}
# Command to run the application
CMD ["node", "dist/index.js"]
Set these four environment variables at startup for the InfluxDB connection.
INFLUXDB_TOKEN='your_influxdb_token' INFLUXDB_URL='your_influxdb_url' INFLUXDB_ORG='your_influxdb_org' INFLUXDB_BUCKET='your_influxdb_bucket'
Once deployed, try a sync. The service should log a successful database write.
Finally, deploy Grafana, add the data source, and create a dashboard with this query:
from(bucket: "bpm") |> range(start: v.timeRangeStart, stop: v.timeRangeStop) |> filter(fn: (r) => r["_measurement"] == "heart_rate") |> filter(fn: (r) => r["_field"] == "avg" or r["_field"] == "max" or r["_field"] == "min")
Enjoy!