I had been looking for how to connect up 2 SENA intercoms with my GPS such that both me and my passenger can hear the GPS directions.
I found that the Garmin Zumo 660 and similar units can pair with multiple devices for audio, but only the last one connected will receive the audio directions.
Also paring it as music did not work as the audio does not pair A2DP profile.
I finally came up with a way to do this so I thought I would share with this group to help out people who want to do the same thing.
The goal for this project was to have the bluetooth audio out automatically start pairing with the 2 Sena units as soon as the bike power is turned on and from then on it should "just work"
My Garmin Zumo is powered off of my motorcycles aux power, as its battery does not have the legs to ride past 4 hours.
The Motorcycle mount has an audio out cable which can be plugged into another device, so I took advantage of this.
I plug this into a bluetooth audio device designed to connect 2 bluetooth headsets to a TV. It was important to find one of these that does NOT have a battery, or even a switch, but connects as soon as it sees power. I selected this device. "https://www.amazon.com/gp/product/B07RKPKWW8/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1"
I also found a SAE electrical connector to USB adapter, to power the above unit off the same AUX power: I selected the Mroinge MSB048 USB charger SAE to usb
I used SAE Y splitters to create multiple SAE connectons to my Garmin and the above unit.
both this unit and the Garmin connections live in a magnetic tank bag, which is connected to the bike power via a SAE cable so the entire unit can be removed from the bike. This also provided a weather proof setup for the Bluetooth device.
We previously had a wired communication system on the same bike using the same powered magnetic tank bag, so going to this one was not much of a change.
My wife and I took the setup out for a test run today, and so far, it "just works".