Or, a simple bluetooth receiver with audio output that connects to a receiver, either via digital or analog connection.
The issue is whether or not your phone (I would probably choose an android powered cellular phone) can be configured to send out audio from calls (not just music apps) via bluetooth or not. It shouldn't be an issue with newer smartphones, since they are often paired with car/external speakers (that of course work with BT receivers).
This rig should give you an idea of what's possible. I believe an Android phone & BT receiver w/ BT 3.0 w/ A2DP is all you need. Perhaps BT 4.0 may give you better range if that's an issue. YMMV.
http://www.androidcentral.com/how-build-your-own-bluetooth-streaming-home-audio-system
Does anyone know of a set-up that will allow me to hear the audio of any cell phone call through my multi-room audio system with the option of hand-held or hands-free for incoming sound (obviously phone required for outgoing)?

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