I have the 660 on my Ultra and I'll defer to anyone that has used the audio output on the Zumo to the Aux in on the bike because I thought that it would only send music.
I use mine with a Scala Rider and I get both instructions and phone calls thru the GPS that way. One thing I noticed was when I linked my phone, a BB Storm at the time the GPS read and stored my call directory on the GPS. To answer calls you just touch the phone icon on the GPS and it links into the Scala.