This project aims to empower ordinary citizens to take charge in collecting real time environmental data that can be used to serve a common interest. The target application of the project is a cyber-physical system for detecting small amounts of explosive vapor in the air so as to protect large-area public gatherings. In this system, extremely low-cost explosive sensors, handed out free of charge, will be connected to the smart phones of the willing participants, effectively turning each one of them into a look-out sensor node.