I am trying to do this too. I have a stock reverse cam (no mirror monitor). I have an aftermarket radio which will take the composite rca input for camera. This is a 2-wire connection (no brainer). I need to locate the actual harness coming from the camera up to the front of the car. Has this been found? I plan on adding a tft mirror later and my stereo will allow for the camera to be displayed on the screen as well as external mirror monitor.
I would venture to say that for an aftermarket stereo the reverse power signal should work for the positive power on the camera (turns on when in reverse only) OR.... the revers light power would also work. Ground is ground.
The other two wires will be the video signal and video signal from a cmos camera is pretty universal. All I would need to do is splice a RCA connector on it and plug it in.
~J~