Several different smart stent structures are described for placement in vessel of a mammal. The stents can be advantageously used to perform measurements of the conditions in the vessel and transmit the measurements wireless out from the patient. In some embodiments, the stent performs therapy within the vessel and may be controlled with a microprocessor, which may or may not communicate wirelessly. Some implantable devices comprise a drug delivery system based, for example, on either a microelectromechanical structure or a cover that opens upon application of an electrical current. Smart devices can be used, for example, the detect deposits in a vessel, aneurysms in the vessel or other modifications of flow in the vessel.