Places! HD app for iPhone and iPad
Continued use of GPS running in the background can dramatically decrease battery life.
Places is the reminder based on your location. When you take a nap on the bus, you may miss the stop. When you visit a new city and take the public transport, you may miss the right stop just because you dont understand the local language.
Set a reminder and put your iPhone in the pocket. The app will remind you when you are close to the destination.