Something Londoners will probably appreciate 
https://play.google.com/store/apps/details?id=b4a.firstoffthetube
Description
Never take the wrong end of the train again! Alight exactly @ the exit you need.
First Off The Tube helps you board the Tube in order to be closest to your exits and interchanges at the chosen station. It incorporates a detailed database of each and every exit and interchange found on the Tube system and works perfectly well while you're underground as it needs no internet connection or GPS information. You can search by line, or just by the station name to find the station you're looking for.
The app also provides information on the closest stations to a number of London's tourist attractions and the Olympic venues
https://play.google.com/store/apps/details?id=b4a.firstoffthetube
Description
Never take the wrong end of the train again! Alight exactly @ the exit you need.
First Off The Tube helps you board the Tube in order to be closest to your exits and interchanges at the chosen station. It incorporates a detailed database of each and every exit and interchange found on the Tube system and works perfectly well while you're underground as it needs no internet connection or GPS information. You can search by line, or just by the station name to find the station you're looking for.
The app also provides information on the closest stations to a number of London's tourist attractions and the Olympic venues
