A system which monitors a vehicle's tire pressures and displays real-time pressure values on a dashboard display while the vehicle is on the road. An electronic unit (100) mounted to the valve stem inside each tire uses a pressure sensor (120) to periodically measure the tire pressure, and uses a transmitter (170) to transmit the measured pressure values, via RF transmission, to a dashboard mounted receiver. The receiver controls a display which indicates to the driver the real-time tire pressure in each wheel. The display also indicates an alarm condition when the tire pressure falls below certain predefined thresholds. The pressure values are compensated for temperature changes inside the tire, and also may be compensated for altitude changes.