I siriusl-ly doubt Sirius/XM would ever consider licensing something like AuralMoon to be played on a subscription service, but hey, you never know. I'm sure Jim would be happy.
I'm still grandfathered on the original AT&T unlimited data plan, and use my iPhone as an AuralMoon receiver piped through my car stereo. The use of AM is almost to a sin exclusively over my own personal music collection, and I have a 64GB iPhone 4S. 3G service is able to play the patron stream almost perfectly. I'm hoping the new LTE service being rolled out cures the holes in coverage I run into every now and then. Once I pickup my new iPhone 5, I'll write again to let everyone know if this is indeed the case.
I've easily used close to a dozen paid radio apps and the one I'm on now is called TuneIn Radio Pro. It offers a roughly 20% accurate album art display that's nice to see. I suppose the accuracy would be better were it not for Jim's oh-so-eccentric music collection.
In this smartphone model, you have to be happy listening to the moon because it isn't always easy or appropriate to fumble to change channels on the phone while you're driving, and of course I don't recommend doing that.