I've actually achieved this on my Z2 although I hooked it up for a different purpose.
I installed a TV tuner into my car and fed the output from the tuner into the AV input and the backup camera input. I did this so I could view the tuner's input basically "split screened" with the map. To get the audio, I'd have to switch to the AV Input. If I wanted to for example put on an NFL game and then listen to one of the XM radio feeds, the audio and video wouldn't necessarily line up but I'd be watching the input from my video tuner and listening to audio from my XM.
So you could do what
