wbwufpack

I recently installed a USA Spec BT45 to enable audio streaming in a 2009 IS350 with navigation. I have been pretty happy with it but it does have one annoying quality. The BT45 connects to the phone and mutes the iPhone's external speakers regardless of whether or not I am using the audio streaming at that time. What this means is that if I want to use the navigation on the iPhone I have to listen to the Bluetooth audio or else I will not be able to hear the voice guidance. I would like to have the option to simply turn off the BT45 when I am not streaming Bluetooth audio so that I can listen to other sources (FM, CD, and Satellite) and use the iPhone's navigation.

Has anybody installed a switch for one of these things yet? I imagine it will be pretty straightforward. I should just be able to open up the wire harness for the BT45, find the red wire, and splice in a toggle switch. Do you guys have any thoughts on this?