Physical inactivity and social isolation are growing epidemics linked to increased morbidity and mortality, particularly among aging Americans. This research aims to address both problems by encouraging co-productive physical activities, specifically walking together. We aim to build an intelligent technological system that 1) connects people in the neighborhood at the right time and place by inferring daily activities and routines of individuals from smartphone sensors and recommending just-in-time co-productive physical activities via smartphones; 2) uses social incentives to motivate people for co-productive activity through recognizing and rewarding real-time activities of a group of people. We hypothesize that this system will increase participant physical activity and social connectedness and improve health.