BigDog.... ;) I am so happy you asked since, thats exactly what I will be using my second webplayer for (emulation via serial ports).
Ok, you know the url for perfect mod, right -- its here:
"Prefect Hack" @ the bottom of this Page Find RS232 Serial Ports. http://www.geocities.com/iopener_hack/prefect/index.html
Now, K-Ray (you ROCK man!!!!) has picture of CN15 and if you look at his pin-outs (Tx, Rx, etc) they are 100% correct, I checked ;) His page is with serial ports is here (I hope its ok I posted it) http://k-ray.netbox.be/?&jq=04010
All you really need is to map the CN12 (i-opener) pin-outs from picture on "PERFECT HACK" to pin-outs on the picture for CN15 (webplayer). The first pin of CN15 is marked on your webplayer with little tiny "1" and then it will look like that
Just map these to k-rays pin definitions and follow the "perfect hack". You will learn that you can use 5V and Ground (power for gps)from the CN15 as well, thats what I am using for my GPS.
Lastly, MAX787 is the perfect thinf for car step down power converter. I ordered the parts already and am waiting impatiently for them to arrive. I will keep you updated of the progress.