I upgraded my raymarine and used one of their simple cameras to give me a rear view. Comes in handing when docking/undocking and maneuvering in tight quarters.
It is connected to my display on the upper bridge and that is the only place I can see the video.
The other advantage is it allows me to see if someone is coming up behind me and to watch the wake and see how the trim tabs are effecting the wake.
All around a worthwhile addition.