Another bump on this for visbility and hopefully some additional useful information. Long story made short I recently got a new car, a Ford C-Max with MyFord Touch, that has Siri Eyes Free capability (as of v 3.6/3.8). Sadly the car I upgraded from had a cheap <$100 aftermarket radio that happily activated Google Now through the standard BT voice dial button and allowed me full hands free functionality and would like to get that back.
What I have found upon a little digging is Apple has published developer documentation which covers Eyes Free functionality:
As someone who can somewhat understand and comprehend this information but couldn't code to save his life, it appears to be fairly simplistic and is just a handful of custom BT serial commands, simple back and forth request/acknowledge commands, and an SCO audio link. Most of the user interface setup seems like it may be on the accessory/head unit end rather than the phone.
I would love to take a whack at this but unfortunately would not know where to begin. My first thought is would something like this with the serial BT communication, establishing an audio link, and triggering Google Now, be able to all be done without root?
If anyone begins on this or also wants to have a go at it, I'd definitely be willing to help where I can including testing and debugging.