Haha! I can't break my NDA becuse I don't know anything official!!!

But my guess is (and it is totally uneducated and uninformed) is that it will tie into the Vista release and will probably be touted beginning of February once Vista is officially in the wild.
We watched a great display/demo of Live Anywhere while at E3 last year. It was VERY cool and should be awesome!!! I imagine (and am not positive) that the extra charges (if any) will simply be the bandwith used on your phone.
I need to find my pics and post them up of this. I had a bunch of them that we took while at the demo. The whole thing is gonna be awesome!