So as to benefit anyone else interested, along with the GXM-30 antenna, I bought this: http://www.revzilla.com/motorcycle/sena-sm10-dual-stream-bluetooth-stereo-transmitter.
Then I attached it via the audio out port of the zumo cradle mount and synced it up to my scala rider g9. You have to disable blue tooth on the zumo though. However, there are two blue tooth audio settings on the zumo either navigation, MP3, phone or just phone. I haven't tried the phone setting yet.