An M-MARK Mk1 device that combines an Inertial Measurement Unit (IMU) with an Mechanomyography (MMG) sensor has been designed and laboratory tested. Novel signal processing techniques have been demonstrated that reduce problems of vibration artifacts and generate information on mechanical muscle activity and movement. The aim of the overall M-MARK project is to develop a low-cost wearable wireless device (Mk2) that patients can use independently at home while practicing standardised everyday activities to regain upper limb function. Mk2 M-MARK has now been developed in collaboration with therapists, patients and their carers. The system incorporates feedback, presented on a computer/tablet, as motivating visualisations of movement showing them if they have moved in the correct way. A separate interface has been developed for therapists, which offers a simple system to diagnose specific movement problems to inform clinical decision-making, monitor progress and thus increase efficiency of therapy.