I just talked to the car guy at my local tweeter store. He said someone was coming out with and adapter that would interface the XM module to the factory radio with a changer style interface..
I will post more when I see one..
P.S.
otisdturner, I am a big IPAQ user. I have a stand that goes in my avalanche cup holder that supports my ipaq and cell phone. I also use the Travroute GPS for the Ipaq as well as GoAmerica CDPD wireless. So I am basically always connected to email while in my avalanche.