Asthma is one of the most common chronical conditions. For many who are affected, it would be necessary to monitor their lung functions much more frequently than by visiting their doctor once or twice a year. Spirometers which measure the volume of air taken in and out whith a breath are expensive and even if you'd buy one, you'd still have to carry another device with you. Smartphones are ubiquitous, everybody carries one - this is what makes mHealth so powerful after all. SpiroSmart is an app that makes use just of the most basic function of any phone: the microphone. By exhaling all your lung's content into the phone's mike at the distance of your full arm's lenght, SpiroSmart calculates the breath capacity. The app analyzes the dynamics of the sound, the exhaling makes to fulfill the task of the classic spirometers that do the same with a small fan that gets propelled by the exhaled breath inside a mouthpiece. The error rate lies close to the parameters set up by the American Thoracic Society ATS. SpiroSmart is developed by an interdisciplinary team at the University of Washington in Seatle. Links: "Tracking Lung Function on any Phone". Poster by E. Larson et.al.