This is an easy project to enhance your layout operation. I've installed what is called a Nanny Cam in inside a box car and use it while switching cars on the layout. This really gives an engineers a down the track type of view. I bought my cam from an ad I saw in Model Railroader magazine. My cam has sound, but sound really isn't necessary unless you're making a video tape movie. Cheeper cams can be found on Ebay without sound.
I put together these four pictures off my 13 inch, TV monitor showing the Mini Cam in operation. When visiting engineers run on the layout, I work as the brakeman operating turnouts and uncoupling cars. The engineer can get the full effect at track view.
It is hard to tell witch car that I've installed the cam into. That is what is so good about this size of the mini cam, it fits nicely into an Athearn, HO Scale, 50 foot box car with a 9V battery. Best to place a flat car in front of the camera car so while switching, the camera is not against another tall car blocking the view.
I installed a small On / Off switch inside the box car door, when the door is slid shut, its unnoticeable and is easy to activate.
Here is what the cam and battery with the shell off. I built up a holder at the end of the car from styrene for the camera to slip snugly into. The camera has an adjustable focus, so this adjustment can be done before the car shell is replaced.