Well you could use a automotive alarm systems. Problem is running the wires. I'm not sure I would worry about triggers for windows. I would look at a motion sensor and or glass breakage detectors. They are set up for 12v
already. 95% of aftermarket alarms have a remote control for arming so no need to worry about drilling holes in the exterior. Some systems have motions sensors. Some have proximity sensors.
The only other problem is placement of the antenna for the brain so that it will get decent signal from the remote. In a car the brain is usualy mounted in the dash so close to the windshield. In a camper you want the brain out of site so your obvious location would be som inside storage compartmet like under the dinnett seats or the under the sink. Not good locations for the antenna. Most alarms the antenna is just a wire of the approprate length hanging out of the brain. There are some that have extendable antennas.
I like Ungo for their very sensative motion sensor. It's not the type that see heat like one in a home, these sense actual motion and could be mounted anywhere like on the floor in a interrior storage cabinet and be very effective. It's a mercury sensor. Down side is strong winds could cause enough motion to trigger and give false alarms. Should be enough motion left that even when you have the stands under the camper that it would still be effective.
Alpine has a good motion sensor like a home alarm that does sense heat movement. Problem is you would need 2-3 of these to effectively cover the windows in a camper. Next and perhaps the bigger issue is these are normaly mounted in the headliner of a car when installed. That presents a major challange in a Airstream.
Glass breakage and other sound sensors can be effective and most better alarms can have them added. Again these can false alarm from things like heavy rain or thunder.