1fast7

There are two companies that are offering these services XM radio(XMSI) and Sirius Sat(SIRI). Both have contract to supply onboard sets to the major car manufacturers next year. You can retrofit their products presently by going to the Circuit City type vendors. There are some differences that you should consider. SIRI owns their satellites and offers more channels that are advertisement free. XM is cheaper at present. SIRI supports NASCAR(had to get that in) and other sports. Can't tell you which has the better reception. Go to any on line brokerage site(C.Schwab,etc) and you'll get plenty of info; esp. SIRI.
Harry