ISS Locator uses your current location to determine when the International Space Station will pass over. Your mobile phones magnetometer is used to indicate which direction to look. The gyroscope is used to indicate the altitude on the horizon where the ISS will appear. A countdown lets you know exactly when the sighting will begin as well as how long it will last. Sightings can added to the calendar or a notification can be set. An email describing the sighting can be sent to a friend.
ISS Locator is a great educational tool and a lot of fun to use.