An airplane's flight data recorder, or black box, saves stats from many different sensors so that pilots can reconstruct and analyze a trip after the fact, whether to find problems or certify that they completed a record-setting route. Now extreme-sports athletes can quantify a wicked ride the same way. Two new gadgets each pack a heap of sensors—GPS to measure direction and speed, accelerometers to measure tilt and pitch, gyroscopes to measure rotation—to record data throughout a snowboard, wakeboard or other sports session. Afterward, included computer software replays the moves on a computer, complete with animated gear; it can also export the files to Google Earth to show paths drawn into actual landscapes. Coaches can use the devices to study and improve technique, and athletes can do something even more satisfying: prove their gravity-defying stunts to pals.