I’ve often wondered if the authorities would care about a community run FOSS plate scanner network that publicly advertised the location of all government vehicles. I mean, it’s public data, right? A nice web front end with built in pattern detection shouldn’t be too bad. Plate scanners can be built with Raspberry Pi’s, so it’s fairly cheap commodity hardware. You’d need a good number though. Coupled with additional hardware, you could put them on cars as well I suppose.