Air quality is a crucial issue for urban environment, urging national and local administrators to implement new approaches and strategies that ensure better environmental governance and public accountability for health. The SensorWebBike is a web-based information service framework designed to support the participative sensing approach [1] for urban environmental monitoring, composed of 3 main components: 1) Arduino-based mobile platforms, installed on bikes, to monitor urban air quality and weather parameters; 2) an Urban GeoDatabase; 3) Web Application, that enables users to view and analyse the data of volunteered geographic information gathered by bikers. The system integrates the analytic and the synthetic method and respects the Open Data approach and the geospatial standards throughout the entire process workflow. Bikers become voluntary “citizens-sensors” [2], and their active involvement could increase the awareness on air quality issues: using their bikes, they populate Urban GeoDatabase with georeferred data of pollutants (CO₂, CO, NO₂, CH₄, O3) concentration, temperature, relative humidity and solar radiation, and contribute to build a comprehensive and constantly updated spatial representation of air quality pattern of the urban area. The SensorWebBike framework is on test in Siracusa (Italy), in a Living Lab operating into a futuristic smart city.