TPMS Wheel Unit Sensor

From LDL Technologies - Tire Watch (or Tyre Watch) is the best solution for motorsport tire pressure monitoring systems.  Made out of high performance material to endure the centrifugal stress on the track. Its simple yet robust design concept allows you to adapt the sensor on all rims for motorsport racing. 

With an internal 3v supply, the typical lifetime of these sensors are two seasons. When the wheel assembly does not have a tire fitted the wheel sensor enters a "sleep mode" to save battery life. When a tire is mounted and pressurized, the sensor will no transmit any data except if programmed for paddock survey.