This paper presents a novel wearable device: the SPHERE Wearable 3. The Wearable 3 is a wrist-worn sensor node tailored for low maintenance residential health and behaviour monitoring. It features multiple inertial measurement sensors, as well as a heart-rate sensor, capacitive button, and OLED screen. The Wearable 3 builds on our experience with previous generations of wearable sensing nodes while adding novel features, including interactive elements. We present a novel two-way communication based on a customized implementation of the Bluetooth Low Energy (BLE) protocol to connect the Wearable 3 with a gateway device, and describe various optimizations of energy consumption. The Wearable 3 is currently being deployed in residential homes in Bristol, UK, as part of a project aiming to collect diagnostic data from early-stage Alzheimer's patients.