ezGear ezTrip TransCharger
I've had bad luck with both of the FM-transmitter iPod add-ons I've tried, for playing music from your iPod on your car radio. It's almost certainly because I live in a metropolitan area and the radio waves are just too crowded for the relatively weak signal from the FM iPod transmitter to come in clearly on my car radio.
ezGear has released the ezTrip FM TransCharger which combines both a car charger and an FM transmitter into one product. If the added power source means a stronger FM transmission, I'd consider buying one. Otherwise, I'll keep using the Griffin SmartDeck. I'd be interested in hearing any feedback on this product from readers who've tried it.