Tensegrity structures represent a special class of tendon space structures, whose members may simultaneously perform the functions of strength, sensing, actuating and feedback control. The paper exploits this advantage, proposing a smart tensegrity sensor for simultaneous measurement of six quantities: three orthogonal forces and three orthogonal moments. The paper shows how the static and dynamic characteristics of the device can be calibrated through pretension and damping adjustment. The external forces and torques of interest are estimated using the measurements provided by selected tendons. A state estimator, based on the linearized model, finalizes the design.