A smartphone application has been created that provides consumers with real-time information about local air emissions resulting from their energy consumption. The purpose of the application is to provide information to enable consumers to consider emissions as they schedule their energy use. This tool provides one mechanism for demand-side optimization through optimal timing of energy use for environmental benefit. The application relies on a model that estimates air emission rates of user-selected pollutants based on real-time spatially accurate information on the electric grid. The development of this smartphone application, its potential use, and opportunities for future improvement are presented.