I fitted a car alarm to my new enclosed trailer.
It sends me a text message if it's triggered. (The alarm wasn't very expensive, and an Aldi SIM is $10)
The trailer would look fantastic with some "Skypig Racing" stickers, but "Sewerage testing services" would be smarter.
Another thing worth considering in the correct circumstance is a baby monitor if your garage is remote for eg. ("Sounds like my bike is coughing, and using a hack saw. I better take this bat/12g out and see if I can help!")
Technology like Cameras with remote connections, and GPS trackers have become extraordanarily inexpensive.