GaitTrack is a phone app to detect health status, while the person is simply carrying it during normal activities. No additional devices are necessary, only smart phone software. The GaitTrack software monitors gait speed, the walking patterns. It uses the phone sensors, accelerometer and magnetometer, to record spatial temporal motion of the phone. Our software transforms the phone motion into body motion. There is immediate application to chronic disease of lung and heart, such as COPD and CHF. A health monitor system using simple phone app can detect variation, individual change in activity status, and assess severity, comparing changed status to normal baseline for a particular level for the chronic disease.