You wil nead something like this
http://www.europeanautosource.com/pr...roducts_id=345
or
http://www.europeanautosource.com/pr...roducts_id=630
so the charger menu is activated and you will get sound trough the adapter.
Then you will have to look for a specific i-bus message when you switch to the charger, so it will give signal to CarX to switch to RV camera input
Theoreticly it is possible, however i dont know of anyone that did it.
Maybe you should try talking to Kiwi he if anyone knows how i-bus works and what the possibility of doing this is