Speedy

An average speed camera anyone can set up. Prop a phone up facing a road, get a mate to do the same further along it, and Speedy reads the number plates going past. When both phones see the same car it works out the road distance between them and how long the car took, and flashes the average speed.

The server only relays plate captures between nearby phones and forgets them after an hour. Match reports and photos stay on the phones. The one thing kept long term is a plate-free heat map of average speeds on each stretch of road, which is on the website.

How it works

1. Capture. The camera runs OCR on the live picture, on the phone. A plate has to be read on a couple of frames before it counts, which cuts out most misreads.
2. Broadcast. Each capture (plate, GPS position, time) is saved on the phone and sent to other Speedy phones within about 5 miles.
3. Match. When your phone sees a plate that another phone reported in the last hour, the two captures are paired.
4. Speed. The road distance between the two points comes from a routing API, not a straight line, and speed is distance over time.