A stand alone device that can track/tell what is the current location road 'live' speed limit.
Best to operate w a cable if not, battery operated if fine too. Small enough to view & place beside speed meter.
I undestand that you have a device that needs to be manufactured. I have in my contacts a company that manufactures small GPS devices to track trucks so I am sure that they could help you. My offer includes making sure that this company can help you with the manufacturing and getting them the plans of your device. For an aditionnal fee, I could also design industrial plans for your device to make sure that it is ready for production. I can also arrange the logistics part for you.