Our chartplotters each support two video inputs. I am the kind of guy that thinks if it can, it should. If there are two jacks there, something should be plugged in to them. So I added a camera on the mast, and another in the engine room.
The camera on the mast looks backward at the stern deck and the area around the stern of the boat. We use this camera often. Whenever one of us is outside on the stern deck while we are underway, the other is watching from the helm.
The camera is especially handy when we are maneuvering around marinas and near docks.