A sensor system (1000) comprises a tag (100). The tag comprises a sensor (110), a radio-frequency chip (130), and an antenna (140). The sensor provides an output analogous to a change in environment of the sensor. It produces an analog output and includes output terminals. The chip comprises a memory element, input terminals in communication with the sensor, and output terminals connected to the antenna. The output of the sensor alters the value of at least one bit in the memory of the chip.
