I have one very similar made by belkin, and my friend has the one made by apple called the iTrip. I wouldnt suggest the iTrip, it seems to always have terrible reception in cities. But the one i have made by belkin works suprisingly well even in cities, and is crystal clear once your out of major areas.
Heard all FM wireless iPod devis are not good.
Too many interference.
Song pops and lack of quality.
Best is with the A/V inputs/outputs in the rear of the deck or tap to the changer connectors. If you have an Alpine deck, it's really friendly.