RFID tags?
What about RFID tags? Are they already detected by driverless vehicles?
If you can make beacons cheap enough then it would make sense to attach them to bicycles and pedestrians, and road furniture, but you'd then have to reckon with there being a lot of unattached beacons: ones that broke off or were dropped accidentally, or left hanging on a string from a branch of a tree by some joker. You could have a beacon that transmits a code that means "this beacon should be attached to a vehicle/bicycle; if found unattached and unattended, please destroy". Then it could at least be disposed of when found in a stupid place. You could also have a code that means "the police know which human this beacon was issued to", which would let you treat such a beacon slightly more seriously as there would at least be some potential embarrassment if a lot of beacons associated with the same person were to be found in stupid places: possible visit from a PCSO or whatever.
Handheld devices to detect beacons would also have to be cheaply available to help people check that beacons are working, find them when they're lost, etcetera.
There's a risk that beacons will be used for spam or graffiti: need to think about that aspect.
Biting the hand that feeds IT
