Speed Watch turns your device into a GPS speedometer with a live map and automatic speed-limit alerts — a full driving head-up dashboard in a single page, with no libraries, no API keys, and no account.
How it works
A large canvas speedometer is the hero: your live speed swings an eased needle around a 270° dial styled after European road signage, with a big digital readout and a green "legal" zone that turns red past the posted limit.
Speed comes straight from the device's GPS through the standard geolocation API — and where the hardware doesn't report speed directly, the app derives it from how far you've moved between fixes, smoothing the reading so a parked device settles to zero instead of creeping.
Alongside the dial, a hand-written renderer paints OpenStreetMap tiles directly onto a canvas (no mapping library) and marks your position with a heading arrow and a GPS-accuracy ring; you can drag, pinch and zoom it, or let it follow you and tap Re-center to snap back.
The posted speed limit is looked up live from OpenStreetMap's Overpass service for the road you are actually on — matched by both distance and heading so a parallel side-street doesn't fool it — and shown as a speed-sign roundel on the gauge. When you go over the limit (plus your chosen tolerance), a "speed robot" chirps a warning, keeps nagging until you slow down, and flashes a SLOW DOWN banner.
What it gives you:
Live speedometer — an eased needle and digital readout on a road-sign-style dial, in km/h or mph.
Automatic speed limits — the posted limit for your current road, pulled live from OpenStreetMap (no API key) and drawn as a European limit roundel. -
Over-limit alerts — audible beeps with an adjustable tolerance (0, +3, +5, +10) and hysteresis, so it warns you without chattering at the threshold.
Live map — a canvas OpenStreetMap view with your heading arrow and accuracy ring; drag, pinch-zoom, follow, and re-center.
Night mode — a dark theme with an inverted map for comfortable driving after dark.
Keep-awake — an optional screen Wake Lock so the display stays on while you drive.
Demo drive — a fake-GPS circuit that ramps up and down over a limit, so you can try everything from your desk with no movement required.
Your preferences (units, alert tolerance, night mode, sound) are remembered on the device. Requires location (GPS) access and an internet connection — the map tiles and speed-limit lookups both come from OpenStreetMap. It's happiest on a phone mounted in a vehicle; flip on Demo drive in Settings to explore it while stationary.