Leveraging several of a Windows 10 phone's sensor APIs available to the Edge browser, this new PWA (Progressive Web Application) delivers your speed in mph or kph - perhaps to check your car speedo, or perhaps to use instead of it? Yes, if you're navigating then Windows 10 Maps also includes a speedo, but this is in a tiny font - this one is huge and readable from anywhere in the car.

From the (super short) Appscope listing:

A tiny no-frills speedometer progressive web app based on Geolocation API, AmbientLightSensor API, and WakeLock API.

The URL to tap on or type in is speedometer.pwa.run .

Of course, you can turn this into an 'app' yourself with PAWA or just pin it 'as is' on your Start screen. Or just add it as a 'Favourite'. It's up to you. If you're confused by the different PWA options then check out my feature here.

Here's Speedometer PWA in action:

Shown here is the PWA in action in daytime on my Lumia (so we know it works) and, right, (from a promo shot on an unknown device browser) at night time, which is presumably where the 'AmbientLightSensor API' comes in. Give it a try?