I kinda forgot to update on my wiring...
This first diagram is how I have the connector wired where the original CD changer connector used to be. I have an 8-pin molex connector here now, just extra I had laying around. I think this connector is actually too small for the wiring in the car, but it's working so far. I would probably suggest a larger connector, with larger pins to accomodate the wire size better.
I decided to use an ethernet cable to make all the connections modular. One end of the ethernet cable goes to the front of the car, the other to the trunk. I cut off one end of the ethernet cable to make routing it easier, and then I crimped on a 5-pin Molex connector like the 8-pin above. I have an RJ45 receptacle that's wired to my iPod dock connector, which of course plugs into my iPod/iPhone.
I used the schematics here to determine what pins I needed off the iPod.
Inside the iPod connector, I put a 500K ohm resistor from 21 to ground to allow the iPod to accept serial communication so we can control the iPod, and I *THINK* I put a 10K ohm resistor from 5V in to both 25 and 27 (USB D+ and D-); this should put 2V on those pins, making the iPod draw 500mA to charge. Notice there is a switch inline with the power adapter, so I can turn off the charger at will (there's engine noise when the charger is on).
Also, I *MIGHT* have the iPod TX/RX lines swapped...I've gotten so confused with all the revisions of this damn thing that I think I might have them swapped. Not a big deal, it's easy to change them.
This schematic is a basic overview of the wiring involved from the iSaabAux board to the car and to the iPod. Not shown is the DB25 connectors I used to go from inside the case to the outside. You can use whatever you want of course, so that's not mandatory.