A biosensing transponder for implantation in an organism including a human comprises a biosensor for sensing one or more physical properties related to the organism after the device has been implanted, including optical, mechanical, chemical, and electrochemical properties, and a transponder for wirelessly transmitting data corresponding to the sensed parameter value to a remote reader. Disclosed embodiments utilize temperature sensors, strain sensors, pressure sensors, magnetic sensors, acceleration sensors, ionizing radiation sensors, acoustic wave sensors, chemical sensors including direct chemical sensors and dye based chemical sensors, and photosensors including imagers and integrated spectrophotometers. The transponder includes an energy coupler for wirelessly energizing the device with a remote energy source, and a control circuit for controlling and accessing the biosensor and for storing identifying data. The energy coupler can be an inductive circuit for coupling electromagnetic energy, a photoelectric transducer for coupling optical energy, or a piezoelectric transducer for coupling ultrasonic energy. The control circuit can be configured to delay, either randomly or by a fixed period of time, transmission of data indicative of the sensed parameter value to thereby prevent a data collision with an adjacent like device. Methods for using an implantable biosensing transponder include the steps of associating the device with an implant, including temporary implants, prostheses, and living tissue implants, physically attaching the device to a flexible catheter, sensing parameter values in an organism, and transmitting data corresponding to the sensed parameter values to a remote reader.