I have a pair of SMH10s running firmware 4.2.1. I have a Garmin Zumo 660 that is multipoint paired to one of the SMH10s. (I also have an iPhone 5 multipoint-paired to the same SMH10.)
When I ride with my wife, I usually establish an intercom conversation that we leave active the entire time we are riding. But when the GPS gives me a voice prompt, the intercom connection is temporarily dropped, and it is reestablished 5-10 seconds after the GPS prompt has finished. This is really frustrating for both of us, as the GPS prompts frequently interrupt me telling my wife where we are turning next. It can get so frustrating that I end up turning off the GPS voice prompts altogether, which then requires me to pay closer attention to the device.
It would be ideal if the GPS prompts were played in the background when an intercom connection is active, and I just discovered in the documentation that this is exactly how SR10 communications are already handled! Audio from the SR10 is played in the background if an intercom connection is already open.
I attached the appropriate page from the SMH10 User Guide with the appropriate section highlighted.
I guess I could buy an SR10 and hardwire it to my GPS in order to leverage this functionality. But that's an expensive solution since I don't have a need for a two way radio, and it also requires me to mess around with audio cables (which is what Bluetooth is supposed to avoid in the first place).
It seems to me that if audio from a multipoint-paired SR10 can be handled this way, then it should be reasonably straightforward to handle audio from a multipoint-paired GPS the same way. That's my suggestion.