Mine (Nissan,2001) wired to the plug that went into the old stereo for the steering wheel controls, and into the power somewhere.
To install the stereo in mine was a bit of a mission, as the factory unit was a Bose, and Bose speakers apparently are only 1ohm (so running an aftermarket Head Unit to them will kill the head unit eventually). I had to remove the Bose head deck, and the Bose 'Amp' in the boot and re-route speaker cables. I also had to replace the Bose speakers.
Installing the head deck was pretty simple, I got a Nissan to ISO loom, and a ISO to Pioneer bit, so that was a piece of cake. The AWSC took a little bit of thinking, but we got it first time round following the instructions on their web page (just had to find the correct plug in the car to connect it to, it doesn't go to the stereo wiring loom. We just cut the existing wires, crimped on bullet connectors and put it all back together).
I'd definitely recommend the AWSC-1 (along with the ISO adaptors - they are cheaper online than at Supercheap). The steering wheel controls are pretty much all I use in-car. Best money I spent when putting the new unit in.