A stent or graft stent energized from an external power source is provided with one or more sensors to sense a parameter, producing a signal that is transmitted outside a vessel in which the stent is implanted. At least a portion of a body of the stent or an insulated electrical conductor comprises a plurality of turns that serve as an RF antenna. An expandable mesh or helical coils that form the stent body may serve as the antenna or it may comprise a separate insulated conductor. The RF antenna receives energy electromagnetically coupled to the antenna from an external (or implanted) coil and conveys a data signal corresponding to the parameter sensed by the sensor(s) on the stent or stent graft to a monitor disposed outside the patient's body. In one form of the invention, a plurality of conformal array transducers are used to produce and sense ultrasonic waves that are affected by a fluid flowing through a lumen of the stent. This transducer determines fluid flow or fluid velocity. In other embodiments, one or more integrated circuit (IC) sensors are used to sense other physical or biological parameters in the proximity of the stent, producing signals that are multiplexed by an electronics circuit and transmitted to the external monitor/power supply.