We present a motion sensor node to support physiotherapy, based on an *imu. The node has wireless interfaces for both data exchange and charging, and is built based on commodity components. It hence provides an affordable solution with a low threshold to technology adoption. We share the hardware design and explain the calibration and validation procedures. The sensor node has an autonomy of 28 h in operation and a standby time of 8 months. On-device sensor fusion yields static results of on average 3.28∘ with a drift of 2∘ per half hour. The final prototype weighs 38 g and measures 6 cm ×1.5 cm. The resulting motion sensor node presents an easy to use device for both live monitoring of movements as well as interpreting the data afterward. It opens opportunities to support and follow up treatment in medical cabinets as well as remotely.
Keywords: e-health; low power; motion sensing; physiotherapy; wireless charging; wireless connectivity.