Now this should worry XM/Sirius/NAB/CRTC/etc
Check out www.slacker.com
It is an on-line radio service that is just about to introduce a satellite radio service using unused channels of Ku satellites. At the moment you can sign up for free to listen on-line. To sign up, you will require a US ZIP code (14092) and an e-mail address. They do list a portable player and car kit under the products section but these are not yet available. Since it is using the Ku band, I would expect the car antenna to be larger than XM/Sirius?