Remon Medical of Caesarea, Israel, is adapting a sound-based underwater communication technique to monitor bodily functions and even administer drugs. Remon’s tiny acoustic telemetry device, the size of a grain of rice, has no antenna or other wires and can be implanted deep in the body. Similar devices that use radio-based signals must be implanted a few millimeters under the skin or, if placed deeper, paired with a controller near the skin for communication and power. Remon’s device is charged remotely using ultrasound: a membrane stretched across a hole in its custom transducer converts sound waves to electricity. By using a flexible, micrometer-thin titanium membrane, instead of a rigid surface, Remon boosted the transducer’s efficiency 1,000-fold. The firm’s first products are sensors that measure pressure in the arteries of patients with congestive heart failure or abdominal aortic aneurysms, which affect more than seven million people in the United States. Future devices might release drugs. Remon has begun human testing and hopes to go to market in 2005.