As we reported a few weeks ago Sirius is now on the iPhone and iPod touch. You can get the the App for free and sign up for a free 7 day trial if you aren’t already a member. The music is streamed over the net, not via satellite, obviously. It also works over 3G (thanks commenters).
Update: the $3/monh doesn’t get you any Sirius premium content like Howard Stern, MLB, NFL and our beloved NASCAR, which is available separately…so this isn’t something to get too excited about.