The problem for having unattended alarms at the camp grounds doesn't do you much good. Who is going to check on your trailer if you are not there... After it happens you will get thrown out for making loud noises haha...
If you have "Call the Police" type of alarm probably would not work well either in a camp ground full of RV's... Won't be easy for the local police to find your trailer... Of course after 15 minutes the intuder will be long gone anyway...
We keep our valuables with us at all times and work on the "Out of sight-Out of mind" for the items left behind...
I do have motion sensors setup on both sides of my trailer that will turn on the patio lights when tripped. I probably would get a note for the intruder saying "thank you for the lights"...
There really isn't much you can do with the aluminum walls the trailer use. You can gain access through the front door with a large screwdriver in most cases... things stowed outside can be grabbed in a heart beat using cut off tools...
Roy Ken