...and what would you use that for?
The N900 would then be used as an FM transmitter from some other audio source. It would for example enable music played from a PC connected to an N900 to be transmitted via FM to nearby radios, like in adjoining office cubicles, etc. Another possibility: a passenger with an mp3 player can use the N900 as an FM transmitter to play its music through a car sound system that doesn't have an aux input.