A dongle-size device to plug in a car audio system

I need a prototype to be designed. Its a flash drive that when plugged into a vehicle audio system, takes over and controls the songs to be played. I tried doing it with arduino. It should read from its own internal memory and be able to schedule between the the files stored in it and even stop or start the radio automatically. It should also be able to communicate over gprs(SIM card slot). Would be great if you have done this before but its okay if you think you can take on this challenge. Please let me know how you think this could cost when mass produced.