This paper describes user testing of a technological system which enables stroke survivors to independently undertake rehabilitation exercises at home. The prototype is based on advanced movement sensors which are worn by the user when performing prescribed exercises. Sensor data are transmitted to a computer which displays the user's movements and progress. The number and type of sensors, methods of attaching them to the user's body in the correct locations, the type of computer screen and the input devices were changed and refined as the project progressed in response to feedback from people with stroke, their carers and physiotherapists. Home-based testing of the system highlighted usability issues concerned with the appropriateness and acceptability of the equipment in domestic settings, the sensors and methods of attachment, and use of, and interpretation of the screen presentation. Users required education as well as support throughout the testing period. Increasing sophistication of the technological aspects of the system over time resolved some usability issues but also created others, as did meeting the aims of improved clinical utility. The interplay between technology development, clinical utility and usability must be taken into account for devices to be successfully developed for practice.