I tried Slacker radio linked to Ford SYNC in a 2011 Fiesta.
It works the same way Pandora operates in the Fiesta. Your phone is the data and application source. The app is locked out in phone.
Controls are by voice command and steering controls. Information from is displayed on head unit.
No set-up or update required on vehicle. App recently updated in the Android Market adding functionality.
Display of Slacker Radio in Ford SYNC, at left, and locked display on Android phone at right while linked to SYNC.