It seems that my idea might not work. After sending an email to iGPS360 iPod module creator asking him if all of USB data between iPod and whatever is plugged in gets forwarded through the GPS, his reply was that that's not the case, since the module doesn't use USB. This answer seems weird to me, why wouldn't the module still be able to forward the USB data through itself even if it doesn't use it, but the creator probably knows his design better than I do. He did say that the USB connector can be used to charge both the iPod and the GPS. If that's really the case, I will have to build some sort of a carPC. But instead of adding WiFi to it, it might make more sense to remove the current iPod interface, replacing it with PC interface and connecting the PC to iPod using serial connector directly.
So my questions are:
1.) Do I still need 3rd party ODB-II module or can I just connect my carPC to my car's ODB-II connector using serial port and forward this data to my iPod?
2.) Is there ODB-II software for Linux or would I still need to run the ODB-II app on my iPod?
3.) If I have to build a carPC anyway, I might as well buy cheaper GPS antenna for it than one for my iPod. Are all antennas the same in terms of reception or are there ones that I should stay away from?