A passive wireless gastroesophageal sensor includes a LC resonance circuit, two or more electrodes and a passive batteryless Radio Frequency Identification (RFID) circuit connected to the LC resonance circuit and the one or more electrodes. The electrodes are configured to measure an impedance within a gastroesophageal tract. The passive batteryless RFID circuit transmits a frequency modulated signal using the LC resonance circuit that varies between a first frequency corresponding to a non-acid reflux condition and a second frequency corresponding to an acid reflux condition based on the measured impedance in response to a signal received from a detector.