Bluetooth input and output to different devices

Thanks, Allen. Your answer does not address what I am asking. I'll try to be more specific.

An aftermarket Bluetooth receiver is plugged into an audio jack for the car stereo.

An aftermarket Bluetooth handsfree unit with a microphone, speaker, and on-button is attached to the sun visor.

The iPhone is paired with both of these devices.

No phone call is active and iTunes is playing music through the car stereo.

A phone call comes in.

I push the on button on the handsfree device and it answers the phone.

iTunes mutes and pauses the music.

Now the difficult part:

The caller hears me through the handsfree microphone.

I hear the caller though the car speakers.

This is what happens when you use factory-installed handsfree Bluetooth interface.

The aftermarket the handsfree device would need a connection from its microphone to Bluetooth audio-in on the iPhone.

At the same time the aftermarket Bluetooth receiver in the audio jack would need to connect to Bluetooth audio-out on the iPhone.

Would iOS 8 support this?

If the iOS cannot support these split Bluetooth audio-in and audio-out connections, then this would be the next best alternative:

A phone call comes in.

I push the on button on the handsfree device and it answers the phone.

iTunes mutes and pauses the music.

The caller hears me through the handsfree microphone.

I hear the caller though the handsfree speaker.

The handsfree speaker has significantly worse fidelity and lower volume than the car-stereo speakers.

When the call ends, iTunes resumes the music through the car speakers.

Would iOS 8 support this?

Thanks again Allen,

It is an advanced requirement that have begun to assume iOS does not support. I think I have another solution to my problem.

I think the iClever® Himbox HB01 will do the trick.

Wirecutters rated it as the best in the market.

http://thewirecutter.com/reviews/best-bluetooth-kits-for-every-car-stereo/

http://www.amazon.com/Wirecutters-HB01-Hands-Free-Convenient-Activation/dp/B00GJ FGE3W?psc=1&SubscriptionId=AKIAJM4NKIQGABP2PIRA&tag=thewire06-20&linkCode=xm2&ca mp=2025&creative=165953&creativeASIN=B00GJFGE3W&ascsubtag=WC28042

I think it works the following way. I have yet to try it myself but plan to do so soon.

It does not talk to the microphone through Bluetooth. It plugs into the stereo's 3.5 mm jack. The microphone is directly wired to the microphone/buttons/Bluetooth unit. You place that unit on your dash where in a location for optimum speech reception. It always connects its Bluetooth input and output to the iPhone The unit's audio output is wired to the AUX port. So it can play music through the AUX port when you are not on the phone. The microphone is always the iPhone's input. The buttons are used to answer or place phone calls, and control the music (pause, skip...).

For me, it will not cause esthetic problems. The center console in my Prius has the USB-power and AUX-in ports. I will run the cable from there, down next to my seat, across the rug, and under to the console near my steering wheel. The chord will be visible only dropping down from the console beside my seat and then from under the console a foot up to the microphone on the console. I will need 3.5 mm and USB-power extender cables to extend its 3' cable. (These two ports must be close to each other.) The extender cables will connect under the dash.

The battery life is infinite. It does not need a battery. It is wired to the USB-power port.

At least, that is how I think it will work.

For my cars that have not AUX ports, I plan to combine it with an FM transmitter that will provide the connection to the radio. FM trasmitters tend to generate some static, but I expect it is the best one can do.

Note, if the stereo is not in AUX mode, I expect you will not be able to talk on the phone or even know when a phone call comes in. You would have to disconnect the 3.5 mm cable from the iPhone to bypass that. This will not matter to me. My music comes from iTunes and streaming. My FM stations stream well and with no static (when I have a cell signal). Radio broadcasts are soooo 20th century. When I don't have a cell signal, all my iTunes music is on my 64 GB iPhone, so even that is not a problem.

Edit: When not in AUX mode, you need to unpair the iPhone to use the phone (including hearing incoming calls). I expect that will be easy (a long push on the mic button).