Convert the mobile phone to....?
 

I'm driving a 560SEL (1990) with a working mobile phone installed...working, that is, if only a phone company would provide service. Anyway, I don't need it anymore in this day of cell phones. Is there anything I can put in it's place such as a global positioning unit, dvd, whatever? It seems a waste to ignore all the electrical going there...it oughta be good for something more useful and practical. Any ideas, everyone?