A wearable article incorporates a sensor device (10) which comprises a sensor module (101) and an input-output interface (105) arranged to send and receive data over a bidirectional line (11). A buffer (103) is arranged to store time-series sensor data. A programmable and erasable non-volatile memory (109) receives and stores an identifier for the sensor device (10). The sensor module (101) generates an inference using the sensor data. The sensor device (10) is arranged to switch between sending, over the bidirectional line (11), data sensed by the sensor module (101) and the generated inference. The sensor device (10) is a single-wire sensor device. The input-output interface (105) is a single-wire input-output interface. The sensor module (101) is a motion, electropotential, electroimpedance, chemical, or optical sensor module. The sensor device (10) is provided in a system comprising a master device.