Not having read every post in the thread, I'm not sure if this has been mentioned. Kenwood has a compatibility check on their website (
Bluetooth Compatibility List | Kenwood Corporation) which allows you to search by both the Kenwood product and the phone to see if it is compatible and with what features. It even tells you if it is a limit of the phone or the unit.
In the case of the iPhone 3G it looks like to phone doesn't support it, but hopefully we will get the option with iPhone OS 3.0.