Hi Pcarhombre,
Yes you can have google maps show up on the HU. First of all you need to install the Pioneer Appradio application on the iPhone. With that you will see what other software they have available for the advanced app mode. When you connect your iPhone via the CD-IU51V AV Cable and launch appradio, it will give you the touch screen to use google maps, INRIX, Motion X GPS (but you have to purchase the license to display to the HU). I personally prefer the look of Garmin's interface so I have a jailbroken iPhone 4S that is running the Displayout app from the Cydia store. It allows you to output anything to the head unit so I use it to display the Garmin software. It doesn't allow for touch screen on the head unit so you have to use the iPhone to control it. Native apps that run in the advanced App Mode will allow for touch screen interfacing with the head unit. Hope that answers your question.
Cheers
Saj