I am really enjoying this thread.
On the subject of reporting GPS location when stolen or just plain driven around:
Have you guys looked at cheap, low-bandwidth cellular modems designed for Arduinos and other homemade Internet of Things?
http://www.popsci.com/bring-cheap-cellular-internet-tiny-devices-sparks-electron
It's about $3/month.
In another vein, there are long range point-to-point radios for digital data available on unlicensed spectrum.
https://hackaday.io/project/17997-s1g-rf-sub-1ghz-radio-modules-915mhz-and-433mhz
This wouldn't require a monthly subscription, and theoretically you could contact your trailer anywhere in town, and ask it where it is.
http://www.aeronix.com/products/915Mhz
https://www.sparkfun.com/products/12030