Background The system informs the nurse about levels of physical activity in the daily living of patients who are using the It's LiFe! tool. The tool consists of an accelerometer that transfers data to a smartphone, which is subsequently connected to a server. Nurses can monitor patients' physical activity via a secured website. Physical activity levels are measured in minutes per day compared with pre-set activity goals, which are set in dialogue with the patient. Objective To examine user requirements and to evaluate the usability of the secured website, in order to increase the probability of effective use by nurses. Method The needs and preferences of nurses towards the system were determined through qualitative research. The usability of the system was evaluated in a laboratory situation and during a three-month pilot study. Results A monitoring and feedback system to support patients in their intention to be more active