Using Touch Pro 1 as a integrated car phone?

Sorry if that title wasn't clear.  Basically, here's the situation: I recently hooked up my Touch Pro 1 to the aux jack in my Mazda, just to use the MP3 player.  But I noticed that when I get a text message, email, or phone call, the sound will play through the car speakers, just like an integrated bluetooth car system.  I answered a call but did not unplug the phone from the aux jack.  I could hear the caller through the car speakers, but he could not hear me.  Ideally, I'd like to be able to either use the speakerphone mic or an auxiliary mic for a cheaper version of a built-in speakerphone system.  Has anyone done this before?  Or any idea how to use or modify the charger/audio adapter/mini-usb part to allow this? 

I did some searching here, but I didn't find a previous answer.  Thanks!