A passive transponder including an integrated sensor is disclosed. The transponder receives an interrogation signal from a scanner, and is operable to transmit identification information and body characteristic information to a scanner. The scanner is operable to receive the identification and body characteristic information and display and/or store the information. The sensor is integrated into the transponder. If temperature is to be sensed, the transponder determines the temperature of the host using the temperature dependent characteristics of the P-N junction of the integrated circuit.