Madrid Metro AR is an augmented reality app for travelers with iPhone 3Gs. It helps you to quickly locate the closest subway stations.
After launching the app, the Madrid subway stops are displayed onto a map of the city together with your current location. Select the closest station and an arrow will help you indicating the right direction.
Then, when you lift the iPhone in front of you, you will be able to see the direction and the distance to subway stations nearby while turning around.
While you watch through your iPhone camera, you will see the subway stops superimposed, the name and the distance to reach them to ease your subway traveling.