I'd be using a Xperia, which should have the right hardware. I recall reading somewhere that the original N900 radio app also works?
I can do command line, but will need some kind of driver on the host side to communicate with the Xperia's modem to dial out. Given my current circumstances, lack of wired tethering may be a hard stop. I didn't completely understand your "Dev mode" explanation. Would this let me use the modem?