At airport security checkpoints in Knoxville, Tenn. this summer, scores of departing passengers were chosen to step behind a curtain, sit in a metallic oval booth and don headphones. The Israeli-developed system combines questions and biometric measurements to determine if a passenger should undergo screening by security officials. With one hand inserted into a sensor that monitors physical responses, the travelers used the other hand to answer questions on a touch screen about their plans. A machine measured biometric responses -- blood pressure, pulse and sweat levels -- that then were analyzed by software. The idea was to ferret out...