An implant includes a pressure sensor, a controller for acquiring pressure data from the sensor, and an acoustic transducer for converting energy between electrical energy and acoustic energy. A capacitor is coupled to the acoustic transducer for storing electrical energy converted by the transducer...http://www.google.co.uk/patents/US6764446?utm_source=gb-gplus-sharePatent US6764446 - Implantable pressure sensors and methods for making and using them
