It kind of does. All modern cars have an "on-board diagnostics" port that devices can plug into to get information about the car, including while it's moving. T

It kind of does. All modern cars have an "on-board diagnostics" port that devices can plug into to get information about the car, including while it's moving. There are various devices you can buy (Verizon has been marketing one called Hum a lot recently) that can connect to the OBD port and do various things with the information there, such as send you a text if your kid is driving it too quickly or if the car is reporting a fault somewhere. This connector is the same one that service garages hook their diagnostic equipment up to to when you take it in. I'd imagine someone clever enough could wire together a speedometer which connects to the OBD's connector and shows a current speed, though I'm not sure if there are compromises on resolution or sampling time or that sort of thing.