I was thinking of putting in the Mot hf850 bluetooth. Would like to rewire the hf850 buttons to use the steering wheels phone buttons.

Does anyone know how/where to get at the wheels phone button electrical connectors in a 2006 A3?

There is no "wire" getting anywhere, is all between the control units. You can either retrofit the Audi kit or forget the buttons.

and can write software to translate the moto functions into CAN.

:)

I am not real familiar with CAN bus hardware. Are their programable controllers out there for cheap?

I haven't opened up an HF850 but since it has buttons. Should be able to use a couple relays for them.

I think it can work. If you can a CAN bus controller, you can read/flip buttons.

The next step is to react to changes in buttons, that means interfacing with hf850. Since there are only a couple buttons on it, should be able to use relays to simulate them being pushed.

The big question is, can you get a CAN controller for cheap.

Another approach would be to use a CAN/Bluetooth interface. I saw one of these, don't know the cost. This approach may take less soldering but be more expensive.

If yes I'm sure you can pick up a CAN controller and build you own circuit for less than $100. If not then you may be out of luck unless you find someone who can. The OEM interface is about $500, please cables, mic, antenna which is another $200. There was one company who was developing an interface for the Parrot to talk with the Audi CAN but IIRC this has never been released for sale.

Not only will you get an easier install... but you'll also get a much better sounding handsfree kit. Ask anyone, the Audi OEM bluetooth sounds better than moto or parrot to the person you're calling.

Two reasons:
1. the adventure
2. it's against my personal principals to pay that much

Kind of like when CD players came out in cars, only a $800 option (when you could buy a whole new stereo with integrated cd for $200). The bluetooth hardware costs are very small < $20 in bulk; The Audi $400 charge is just repulsive.

I'm looking at a new A3 Sport DSG, NAV, but no Bluetooth. Any information on how much work it is to retrofit the factory BT Module to this car?

The dealer wants $900 for a local car stereo place to hack a 3rd party BT in. FFC.

Search on navplus.us for A3 and Bluetooth and you will find some answers.