A spirometer can measure how badly your asthma, etc, is affecting your airways by simply measuring etc the speed and volume of air as someone blows into a tube.
But SpiroSmart takes a different approach to avoid the need for extra hardware. The researchers modelled a human trachea and vocal tract and used that to generate an algorithm which can analyse the sound of someone's breath as it resonates inside their lungs. The sound and resonance changes as the flow of air is restricted, and the app is able to detect this, providing a doctor with everything they'd need to know to make a diagnosis. Surprisingly, the app, which could be given away for free, is just as accurate as dedicated spirometers. And patients don't have to push themselves to the point of exhaustion just to get an accurate reading. [Ubiquitous Computing Lab - University of Washington via Medgadget]