The valve stems on the wheels of automobiles can be turned into a self-powered, electronic pressure sensor which can send pressure data to the car or cell phone to alert the driver to changes in the tire pressure. This would provide an early warning for any flat tires, low pressure or overpressure situations. Also, by maintaining proper tire pressure, the automobile's fuel economy would be optimized, saving the user money. The design is simple and the cost minimal but the savings in fuel, money and time is large. The power would come from a swinging weight pendulum, similar to a self powered watch, this takes advantage of the tires rotation to provide power for the life of the valve stem. Data could be transmitted by simple blue tooth wireless data transmission and the pressure sensor is a strain gauge that measures the pressure force against the inside wall of the valve stem. Future cars can have the blue tooth receiver built in and send tire information via cell phone to the user so that a low or flat tire warning would be received before they are near to car to see it. The market for this product is in the millions for new cars and replacement tires could add this feature and a cell phone app is all that is needed to make it work. The valve stem would also contain a small rechargeable battery to keep it running while the vehicle is not in motion. This technology would work is all vehicles of any age from classic cars to modern cars and trucks. The weight increase would be minimal and wheel balancing would fix any issues.