To use Bluetooth you would need the Bluetooth module from Harley and I don't think they make them anymore. I have only seen one for sale on ebay in about a year. Not sure why they quit makeing them.
I would imagine they quit making it because there would be a lot of money lost. Think about all the add-ons they have now: Navigation, XM, Ipod, etc... You could have Bluetooth and take care of all of that at once.