iPhone as a physical activity measurement platform

iPhone is emerging as a ubiquitous physical activity measurement platform due to its incorporated accelerometer sensor. The iPhone's capacity to accurately measure physical activity has not been put to scrutiny up to now, despite claims from an increasing number of applications. This study examines ways to perform accurate physical activity measurements with the iPhone, at various positions on the user's body. The study focuses on walking and running - the two most prevalent aerobic activities. For walking, a methodology has been developed that translates accelerometer values from peripheral body locations to equivalent readings on the waist and from there to metabolic units. For running, the limitation of iPhone to perform accurate metabolic measurements is documented. The formulas and results in this paper can readily be used by developers to increase the accuracy of fitness applications and improve user experience.