Pairing modern day technology with Azjen’s popular Theory of Planned Behaviour, the objectives were to i) determine whether a mobile connected activity-tracking device could change physical activity (PA) health behaviour, ii) test whether the theory of planned behaviour (TPB) could predict participation in physical activity, measured by mobile technology, iii) determine if PA engagement is correlated with mobile communication usage and vehicle journey time. Participants consisted of 41 males and 28 females (N=69), each completing standard TPB measures at baseline. Intervention included a health warning/advice sheet and the physical attachment of an activity-tracking device paired with a mobile application for the duration of two weeks. The data retrieved included the participant’s daily steps count, the participant’s daily time spent travelling by motor vehicle or not, and the participant’s daily amount of mobile communication usage time. A statistically significant increase in activity was observed in the device-wearing group, with a medium effect size. Findings did not support the TPB as a predictor of PA engagement in a technology intervention context. There was no statistical relationship between PA participation and mobile communication usage or vehicle journey time. Findings suggest a basis for developing interventions to include mobile connected devices for improved behavioural health.