Yup, Carl L is ABSOLUTELY correct about the dog. Even take one step further, place a BIG dog watering bowl and a HEAVY dog leash chain right outside the door where anyone can see it..... I used to "carry" but varying State Laws are difficult to comply with. I then started to "carry" a 12ga Pump Action Shotgun, but this option only works when you are physically present in the RV. Only have had 1 incident in 50 years of RV-ing where the mere sound of a "wracking" pump action made the would-be thief run like hell.
As I see it, there are 3 scenarios where alarms are useful............ When you are inside the parked RV, when you are away shopping from your RV, and long term storage for your RV.
It would be nice to have a system that would cover all 3. The most difficult, as I see it, is long term storage assuming that the storage facility does not have some type of security. Without re-charging the batteries in your toys, the parasitic draw on them will discharge the batteries during the long term. I use multiple, small solar trickle chargers on everything (RV (House & Staring), ATV, Golf Cart, Lawn Mower, etc). Remotely locating these charger panels in a window works just fine.
So, knowing that the trickle charger will keep the RV (House & Starting) batteries charged I now use a design of my own (previous life as an electronic tech) which basically a 12vdc Ice Cube Relay, 12 vdc Motion Detector, 120vac tape player, a 120vac siren, and the existing porch light. Basically it works like this........Motion Detector (powered by 12vdc) senses movement (either inside or outside) and energizes the Ice Cube. an output from the Inverter (already installed) is fed through contacts of the Ice Cube to a standard 120vac receptacle. Alarming devices (lights, pre-recorded barking dog, loud radio music, siren, etc) are plugged into this receptacle.
It's all hooked up and ready to go. It gives DW peace of mind (which gives me peace of mind, if you understand), although I never have had it alarm in a "situation"........ In closing, and after 50 years of enjoying the tent/trailer/RV life style, I have found your security is basically common sense. Listen to your gut, let your vibes dictate your re-actions. IF a thief really wants something NO AMOUNT of security devices will thwart them...........