Tire Pressure Monitoring System, or TPMS, continuously watches inflation pressure and temperature, and warns the driver of abnormal conditions via an in-cab liquid-crystal display and alarm. The wireless system uses sensor-transmitters that easily screw onto valve stems so tires needn’t be demounted, as they must for installation of internal sensors. TPMS’s sensors have built-in valve stems which allow airing up or down without removal of the sensors. They are powered by batteries with a life of seven to 10 years, and the rugged devices should last indefinitely, according to the company.