Today, there is a lack of useful visual presentations of data showing progress over long time periods for users of physical activity self-monitoring devices. The aim of this paper was to present a novel theoretical model that describes the relative change in physical behavior over time and to provide examples of model application with previously collected data. Physical behavior, which includes both sedentary behavior and physical activity, was categorized into four dimensions and further processed and adjusted to fit the novel model. The model was visualized both theoretically and by using example data for two out of 20 participants, illustrating the relative change compared to baseline and trendlines for all dimensions. This approach to a novel device agnostic model can visualize the data over time and is intended to be used on an individual basis by users that need support for physical behavioral change. The model, which is based on earlier research, has flexibility and was developed to be used as a complement for data processing, to future and currently available self-monitoring devices within this arena. In the future, the novel model should be studied to see if it is valid, tested with larger samples over longer study periods, and tested for use with other self-monitoring devices to ensure its usefulness and trustworthiness.