I'm thinking of the ability like DVRs have for television. Rockbox would "pause" the currently playing radio station and record up to 30 minutes (space permitting) while paused. You could continue listening at any time during those 30 minutes and continue from where you left off. You could use the left << or right >> buttons to move through the "paused" content -- to skip commercials and the like. It would spool so as you were listening the NEXT 30 minutes would constantly be recorded. Recordings would be automatically deleted when you change the radio's channel. Perhaps a warning could be given: "You have saved radio programming. Changing the channel will erase this saved radio programming. Do you wish to continue?"
One potential problem -- players that sleep. My sansa 250r doesn't sleep while listening to the radio, however.
I really wish my car radio had this feature 8-)
Thanks!
P.