i was going to suggest logitech's unify option.
but it appears to be proprietary.
My new install is wireless, using an inexpensive bluetooth audio device to the head unit. However, I have more than one source of music in the car that can connect using bluetooth and wondered if there are devices that allow more than one connection for audio. For example, on e device might have music on it and one might have the gps turn by turn instructions on it.
I haven't seen this and was wondering if anyone else has?