As a former physical security professional (& a lot of other things too)
I suggest a big dog - the meaner the better and a perimeter of claymore's. Usually works. Be sure to point them away from your trailer, range is limited to 300 ft - or so.
You can take out a whole neighborhood if you're not really careful.
Evidence of forced entry is necessary to keep you out of the pokey - so create it before the law arrives.
Punjii pits are also an option.
When all else fails - a little caution and situational awareness works for most people.