Jim...can you hear the GPS commands on a regular BlueTooth headset?? I really don't think your gonna hear those instructions thru the BlueTooth...I have text messages sent to me that usually set off a ring just like a call coming in (different tone of course) and that doesn't make it across. I think the system is smart enough to know the difference.
It's actually going to depend on the protocol of the particular audio output source. If the phone/device does all it's output on a protocol (a2dp, etc etc etc) "heard" by the Bluetooth you'll be good.
I had to get a new phone recently. Got a real common device. One of the Motorola Razr V3i units. It was red and it was surprisingly cheap. The V3i variant has an integrated digital music player. With 2 gigs of memory in it the phone could double hit as the MP3 player or iPod that so many carry. It even does the job quite well and surprisingly easily. But.....
But the Bluetooth is hinky. Whomever was the systems integration engineer didn't do his job. Get it in range of a Bluetooth receiver (in my case the vehicle or the motorcycle helmet) and the phone's audio doesn't play locally (as one would expect). That is all the phone's audio.
Trouble is the phones "phone" audio and it's music audio from the digital music player transmit over two different protocols. The one for the music audio is picked up by no Bluetooth receivers. No way in the phone to disable BT output for the music player either. So if you're in the vehicle there's no tunes from the phone. This is even the case with the new Motorola phone and a new model Motorola vehicle unit. So Harley isn't the only one to do stupid stuff (they just work at perfecting the skill).