I vote for a manual switch. That way when you need/want to see the rear view while moving forward you can.
Nothing like having to put it into reverse to powerup the camera when you just need a peek.
There are lots of low cost cameras out there that you can put anywhere. The most important feature is the ability to reverse or mirror image the view. This can be done on some cameras and on some monitors.
BTW when faced with the choice between a CCD vs. a CMOS camera the image will be much sharper with a CCD.
1984 28' Funeral Coach
Former Rolling Showroom & PuttLab (now party bus)
"I'm not an expert. But I did sleep in an Airstream last night."