A wireless sensor includes a radio frequency (RF) front end and a sensing integrated circuit (IC). The RF front end includes an antenna that is operable to transceive RF signals and a tuning circuit. The sensing IC includes a power supply. The sensing IC is operable to detect an impedance change of the power supply. The sensing IC is further operable to convert the impedance change into a digital value. The sensing IC is further operable to output, via the antenna, the digital value.