The Sentinel System with Tracking App from GiraffeG4protects trailers from low-clearance collisions with two parts: A tracking app that measures the heights and locations of potential low-clearance hazards between 9’ and 20’, and a user app which warns drivers before they reach a hazardous area. The full Sentinel System and app includes a weatherproof sensor, a Bluetooth-enabled data collection module, and a 12V plugin. It also comes with the GiraffeG4 Tracking App (for Android phones only) and a mount for the Tracking vehicle.