An apparatus for monitoring a vehicle condition comprises a sensor for sensing the vehicle condition and a transmitter for transmitting signals indicative of the sensed vehicle condition. The transmitted signals include a first signal set and a second signal set. A receiver mountable on the vehicle is provided for receiving the transmitted signals. The receiver has a first operating state when the vehicle ignition is OFF and a second operating state when the vehicle ignition is ON. The first signal set includes a wake-up portion to wake up the receiver when the receiver is in its first operating state and an information portion. The second signal set includes an information portion. The transmitted signals include at least one first signal set and at least one second signal set during a predetermined time period when the vehicle ignition is OFF and when the vehicle ignition is ON.