Looks like General Motors is up to something. In a recent U.S. Patent application, GM has spec'd out a method for "customized music delivery" to vehicles. Here's the abstract first:

A system and method for customized music delivery to a vehicle including determining a playlist, storing the playlist on a server, selecting content corresponding to the playlist, transmitting the content to the vehicle by satellite, and storing the content in a telematics unit. 

The overall concept is that the user would be able to create a custom playlist that is stored remotely on a server, and access that playlist - via satellite - anywhere in your car. They specifically cite SDARS and give several examples of usage (including video). The integration could be with the 'telematics unit' either connected to the vehicle's satellite radio receiver, or embedded within.

It sounds like a great system. GM would be solving all the connection problem that people have had with iPods (to the point now that an iPod cord is considered a "feature" in some cars now). My only concern would be with how human's would interface with the system. Selecting a playlist while driving could be a pretty dangerous endeavor.

Unless... XM has already solved this problem.

Thanks Tim!