At the 2017 SHOT Show, I was stopped by a nice young lady who then told me about GunAlert, a handy little device you can attach to most any item (in her example, a handgun on display at a gun show) that will alert you if someone takes the item away.
GunAlert is a small device that you attach to your gun (or whatever) using a zip-tie or other similar method. The device uses Bluetooth to communicate with an app on your smart phone (or other Bluetooth-capable smart device). If the device moves more than about 20 feet from your phone, it begins to blink and beep and your phone also sounds an alarm. So much for the five-finger discount a thief thought he was about to receive.