Sirius already have their satellites up, testing and demos happening.
There standard antenna looks like a hockey puck or tear drop. And the special antenna is required to pick up satellite signals.
XM owned by GM are followers. Still waiting on satellites, antenna, etc. Expect XM no earlier than end of this year if not next.
Sirius may be available this summer.
It's great for people with no or poor radio stations and they actually listen to radio.
