An alerting system for signaling the displacement of a leading end portion of a hose or the like, carried by a vehicle, includes a hose-gripping unit, a visible or audible signal generator, and a mounting box for connecting the gripping unit to support structure. Displacement of the hose from the gripping unit may generate an alarm signal to enable the operator to immediately bring the vehicle to a stop, or it may generate a signal simply to indicate when one of several hoses has been intentionally deployed.