Ingenico, a French company, has devised a way of embedding payment information in an MP3, and they're even working on boarding passes and biometric information. Now I don't know much about the inner workings of FM, but isn't it a broadcast technology? Meaning: wouldn't anyone be able to receive anything you transmit out through your iTrip?
Minor complications aside, at least Ingenico recognizes the pointlessness of this, as stated in a press release: "While this demonstration may not be a sign of what the future holds, it certainly proves Ingenico's ability to innovate for the benefit of its current and future customers." Translation: "This is completely useless but hey, aint we%uFFFD cool?" Hopefully, we won't hear anything like this out of Apple again anytime soon (*ahem*, ROKR).