Hi. The USB radio stick(s) tend to be poor in car environments. The radio(s) in question are DirectedHD and Visteon. The can be controlled over a serial port.
I have been searching, and so far, the best (I think) is either a library package that will allow communications via a USB / RS232 adapter, or a bluetooth RS232 adapter. The bluetooth adapter HAS to support DTR signal. From what I see, those tend to round $80-100. The library allows using the serial adapter via USB host mode that Android now supports. And does this without requiring root priviledges.
That's a quick summary of what I have found so far. I'm not sure if any driver would be required, but a radio application that knows how to talk to these radios, via the com port, is what I think is required.