You have no idea what you're talking about!!!!!!

Parrot CK3100 requires:
LIVE
SWITCHED LIVE
NEGATIVE/EARTH

Audio inputs and Audio outputs, ideally it also requires a mute signal- but the relay in the parrot kit is quite clever and it is not neccesary.

Modern car stereos work using LIVE and NEGATIVE the on signal comes from CANBUS which is activated during vehicle ignition (or in some cases fibre optics/infra red) this is digital signals in the form of a pulse and tell the stereo what to do via these pulses.
IE ON or OFF

http://www.powerbase-auto.co.uk/canbus.htm

They carry little or no voltage and certainly not enough to power something off of and the fact they pulse means even if they did they would not work

In fact messing with these would possibly damage other systems on the vehicle.

The ONLY way this guy may be able to use the back of the stereo is IF the CANBUS switchs on a redundant switched live for the likes of a power aerial or for a cd changer- however as the chap in question has already stated he wants plug and play due to potential warrenty issues this is not an option.

DIY
DAMAGE IT YOURSELF