The number of sensors of all types installed in vehicles and industrial plants worldwide for operational safety and process control is in the billions and increasing exponentially. Historically, sensors have been linked by cables to electronic modules, which provide excitation, amplification, signal conditioning, and display. There are severe problems, however, when sensing parameters such as strain, pressure, torque, and temperature with sensors mounted on rotating components or operating in hazardous or extreme environments. For these applications, wireless sensing is advancing rapidly.