Sirius radio comes to the iPhone with uSirius, an app by Millard Software which allows you to log in to your Sirius account and listen via the iPhone. Still in beta, the app can be downloaded from their repo at
They do warn that initial loading of the Channel Lineup and Channel Logos takes a while, and the app "may even cause your iPhone/iPod Touch to reboot." But hey, its Sirius, on the iPhone. Serious.