Dementia is a common affliction in the older adult population and often causes difficulties in remembering the required sequence of steps needed to complete a task. The current solution is to rely on a caregiver to supervise the person with dementia through the task, correcting their actions as necessary. However, maintaining independence from a caregiver is essential in promoting feelings of dignity and reducing caregiver burden. This paper presents the iterative development of a system that autonomously guides people with dementia through the task of handwashing. Clinical trials were used to evaluate each prototype and identify deficiencies that were resolved in subsequent prototypes. This approach has resulted in more effective, robust and unobtrusive task-tracking and subject interaction. The system has reached a point where it is ready to be tested with other activities (e.g. tooth brushing), populations (e.g. children with autism), and integrated ubiquitously into a smart-home.