SirenGPX

Overlay your speed, heart rate and route — from Apple Watch — onto your ride videos, rendered right on your phone.

Available on App Store Coming soon to Google Play
No spam — one email when Android launches.
What it does

Turn ride data into video

Apple Watch

Pull workouts straight from Apple Watch via Apple Health — no third-party account needed. Heart rate, speed, route, altitude and more, right from your wrist.

Magic Sync

No manual alignment needed. The app automatically syncs your video with the workout based on timestamps.

📱

On-device rendering

FFmpeg burns the overlay into your video locally. Your footage never leaves your phone.

8 speedometer styles

From minimal to bold, pick a speedometer that fits your edit — fully positioned where you want it.

🗺️

Advanced Scenes

Add a real-time track map, elevation profile, or a digital bike computer overlay to your video.

📊

Rich metrics

Visualize Heart Rate, Altitude, Distance, Gradient, Cadence, and Power in real-time.

🔒

Secure & Private

Read-only access to Apple Health. Your workout data and videos never leave the device — no accounts, no cloud, no uploads.

Real app

See it in action

SirenGPX matching a gallery video to a workout
Your video is auto-matched to the right workout.
SirenGPX studio: speedometer style and metric layers
Tune the speedometer, metrics and layout in the studio.
How it works

Four steps to a finished clip

1

Allow Apple Health access

Grant read-only access to Apple Health — the app picks up your Apple Watch workouts automatically.

2

Pick a video

Choose a clip from your gallery — the matching workout is found for you.

3

Customize the overlay

Choose the speedometer, metrics, scenes and position.

4

Render & save

FFmpeg renders on-device and saves straight to your gallery.

Data

What you can overlay from Apple Watch

MetricApple Watch (via Apple Health)
Speed & distance✓ GPS workouts
Heart rate✓ from the wrist
Altitude, gradient, map✓ with GPS route
Cadence & powerwith sensors (iOS 17+)
Temperature

Works with any outdoor GPS workout — cycling, running, hiking, skiing. Indoor workouts without GPS can’t provide speed or a route.

Pricing

Simple & transparent

Free

$0 / forever
  • 5 speedometer styles
  • Basic metrics (HR, Distance, Altitude, Temperature)
  • Mini-map, Elevation graph, Speed graph, Cyber, Grand Tour, VHS Tape scenes
  • Magic Sync & On-device rendering
  • Includes a small watermark
  • Pro metrics (Power, Gradient, Cadence)
  • Pixel Racer theme

Pro

$4.99 / one-time
  • All 8 speedometer styles
  • All metrics (Power, Gradient, Cadence)
  • Pixel Racer theme · exclusive
  • No watermark on exports
  • One-time purchase, yours forever
FAQ

Frequently asked questions

Which cameras and video formats are supported?

Any video in your phone’s gallery — footage from the phone itself, GoPro, DJI or any action camera, once it’s imported to the gallery. The overlay is matched by the time the video was filmed, so make sure your camera’s clock is set correctly.

How does syncing work? Do I need to align anything manually?

No. The app reads the video’s creation time and finds the Apple Watch workout that was running at that moment. Speed and metrics are aligned to the second automatically.

Are my videos uploaded anywhere?

Never. Rendering runs entirely on your phone with FFmpeg. No accounts, no cloud, no uploads — see the Privacy Policy.

Why is a metric greyed out?

That workout simply doesn’t contain it: power and cadence need sensors, heart rate needs a watch or strap, the map and altitude need a GPS track, temperature needs a thermo sensor.

Is Pro a subscription?

No. Pro is a one-time purchase — pay once, keep it forever on your platform. Refunds are handled by the App Store / Google Play under their standard policies.

Your data stays yours

No accounts, no servers, no uploads. Apple Health data and your videos never leave the device. Read the full Privacy Policy.