Unhealthy diets have overtaken tobacco use as the major risk factor for disease in New Zealand. To date, the pressure for action on reducing obesity and diet-related non-communicable diseases (NCDs) has been predominantly elite (i.e. health professional driven), not grass-roots (i.e. public driven), and this is part of the reason that there has been insufficient policy action. This project will develop and test approaches to engage and empower citizens in New Zealand communities through: 1) crowdsourcing data with a smartphone application on nutritional quality of foods in schools, outdoor food advertising, food advertising through sport club sponsorships and events, food retail, and local physical activity environments; and 2) tailored feedback about the healthiness of food and activity environments to citizens, councils, local Members of Parliament, schools and retailers. This will support public awareness, sustainable monitoring and actions at the local level in New Zealand to reduce obesity and diet-related NCDs.