1. A mobile apparatus comprising: an inertial sensor to monitor accelerations; a motion processor to identify a user activity based on the accelerations and to make a first estimation of a user activity statistic associated with the user activity based on the accelerations, the user activity statistic being a distance traveled, the motion processor further to calibrate a stride length correlation model based on the accelerations and the second estimation, wherein the stride length correlation model is used to make the first estimation; a location based sensor to obtain location information; a location processor to make a second estimation of the user activity statistic based on the location information; and a calculating logic to calculate the user activity statistic based on the first estimation and the second estimation, wherein the calculated user activity statistic is a result of a weighted combination of the first estimation and the second estimation.