The invention device monitors the pressure of a measurement chamber subjected to the pressure prevailing in a vehicle tire. A pressure-sensitive device scans the tire pressure with a pressure measurement member in a measurement chamber. In case of a tire-pressure drop, the tire pressure is used to actuate an auxiliary actuator (3, 24, 26). The auxiliary actuator genrates the regulating distance (s) dependent on a tire pressure drop below a pressure value required for an actuation of the actuator (13). The regulating distance (s) is recognizable by a sensor. The invention device is suitable for providing a permanent signal even in case of an absence of pressure in the measurement chamber (21).