I know it can be done with the PS3 using a tool called SiriusXMStreamer. I have successfully run it this way. uSirius still works, as far as I know, but you must have had it setup already (as you cannot download it any longer). You will need TVersity as well, as the server, if you use uSirius method. SiriusXMStreamer acts as a server too, sot his is a stand alone option. In addition to these, you can try Orb, which I have had some luck with.
I tried to use Orb to stream Sirius from a computer to my Droid. Technically tricky and a pain, really. I would go with SiriusXMStreamer for the XBox method.
Something else you may want to look into for streaming video is PlayOn. You can stream Hulu and other TV content with this tool - it's cheap too, like $30-40.
There are not many posts about PS3, XBox and streaming on this board. Kinda quasi-relevant, actually. According to the FAQ, though, it seems legit. Good question!