If that's an illuminated toggle switch, it will need the ground. You could also switch that lead so you can control that light as well.
You never know when the bike courier is riding you!Shane
Fluf has rear windows that have unobstructed view most of the time so I use my camera as truly a backup camera. Having said that I have had two motor-homes that have had cameras. On the first one, due to longevity considerations, I intended to use it infrequently to check on my toad. It didn't take long to realize the value of full time operation. I now run it 100% of the time in my current motor-home because the camera will at times pick up vehicles that the mirrors don't. The mirrors are primary, camera secondary and it provides just a little more info as to what is happening around me.