According to statistics (which are wrong nearly 50% of the time) the two biggest deterrents to thieves are the owner may have guns and dogs. I suggest getting a couple NRA bumper stickers for the first, since they work even when you are not there, and it sounds like you have a couple dogs.
Pretty much any 12 volt car alarm can be fitted to an RV as long as you have power to it. They will run down most car batteries pretty quick, I know if mine sits for more than 10 days on, then I need a jump or charge. Look for something with door switches, you can decide how many. Most are expandable, so you could mount more switches in baggage doors etc. I have given some thought to doing this, and may in the future.
2013 Coachmen Freedom Express 320BHDS pulled by a 2005 F250 King Ranch CC
A rainy day camping is better than a sunny day at work.