I use the X10 HOME AUTOMATION products on my OFF-ROAD POPUP setup..
X10 Home Automation
They have an excellent motion detector setup that runs on BATTERIES and will react with a indoor controller unit to turn on lights and things... Has a good 80 foot or so range.
I have two of these motion sensors on both sides of my popup and they turn on the patio awning lights when you walk up. They also are control by a pocket FOB unit.
I also use these inside the trailer for night lights so to speak... I have a couple of runs of the ROPE LIGHTS behind my valance curtains going around the inside of the trailer. I can controls these lights as well with the remote control unit laying by the bed...
These sensors are mounted on both sides of my POPUP trailer using velcro tape...
Also these remote control 120VAC receptacles units are handy to have in the trailer. Great for turning on /off lamps etc.. Got from local hardwarestores.