Valker is a free, light-weight application for walkers. Valker lets you map and track your walking workouts. Using the GPS on your iPhone, Valker will show your progress on a map, and track distance walked, pace, duration, and calories burned. It stores your previous workouts on your iPhone, for your review. You can also view your workout history in chart form to help you visualize your progress. Supports both street and satellite maps. Runs in background so you can listen to music or audio books while you work out. Walker is self-contained on your iPhone. There is no need to register or visit a web site. (Note: Continued use of GPS running in the background can dramatically decrease battery life.)