This can be done on most cars with factory installed backup cameras. If your camera currently shows on the radio screen itself, you will most likely have to send power to the camera as well as catch the signal wires. Some cameras are 6V DC and not 12V, so you will need a voltage step down like the Metra Axxess AX-CAM6V.
I’ve done this on several cars successfully including a couple of Toyota Tundras and Chevy trucks. Here is how I did it on my wife’s Subaru Forester XT:
First thing you’ll need to do is cut off an end of an RCA cable with enough slack to run up to the camera connector. Strip back the insulation and separate the signal and shield wires. I forgot to take a picture of this, so I stole this one. I would recommend using a high quality RCA cable for this as cheap ones usually fall apart when you strip the insulation back.
On my 2015 XT, these are the wires you’ll need to tap into. The shield is the translucent blue wire, and the signal is the black wire. This is the 8 pin connector on the back of the multi function display.
Make secure connections then plug the RCA into the backup camera input on your new radio.
You’ll also need to run a separate wire to tell the radio when you’re in reverse. On my car, it’s on the driver kick panel. Brown/yellow wire. Just splice into that and run it up to the reverse wire on the radio harness.
There you have it. Backup camera image mirrored onto the radio screen.
Also, the iDatalink Maestro is awesome and gives you gauges and steering wheel controls in one on select cars and radios.