Nexus 7 camera mod

so i have a Nexus 7 mounted in my car that i use for google maps and for media. it's connected via bluetooth to my audio processor (rockford 3sixty.3) 

i have been trying to think of a way i could hack this. and the best thing i've come up with is to take it apart and either  remove the camera extend the wires and actually mount that camera on the rear of my car for a backup camera or maybe figure out a way to pipe the video from a different backup cam into the nexus 7. 

and to trigger it i was thinking i could maybe map one of the buttons, to open up the camera app. maybe the volume down button? and to trigger the button i would open it up attach the connection points of the volume button to a micro relay. i would trigger the relay by using the reverse lights on the car. 

if any one has any experience or has even been inside a nexus 7 feel free to chime in. i haven't even opened mine up this is just kind of a brain storm.