I have two headrest monitors. Right now i have them hooked up, so when i play a video on the D3, i can see the video on the monitors. But is it Possible to see what i am seeing on my D3 (when its not playing a video) on those monitors. I know you can do this with Alpine but im not sure about Pioneer.

On the Z series you can change the video output to show what is being displayed on the headunit. This setting is called "mirror". You don't have this feature on the D3.