London Tube Stations
 

http://londonist.com/2013/06/stationmaster.php

Helpful

If you'd rather not pay 2 quid, and/or want it to work on a non-iOS device, then the 3D maps produced by Andrew Godwin are worth a look. He hasn't done all of them, but he has a lot of the key ones done, and the technology behind it is interesting too!

Interesting, perhaps, but helpful?

Well it might be for people who were mobility impaired or who are carrying luggage or who have to push a baby carriage around, since it could, potentially, help people to pick parts of the train that involve the least walking at interchanges or exits and, in some stations, help them to decide on the best way to make an interchange so as to involve the least stairs.

Interesting, definitely, and (IMHO) helpful if you are not familiar with the London tube system. There is far more to the app than simply maps of tube stations. There is detailed information about facilities available at each station as well as related bus line information and more. As a visitor I find it very helpful, even after many visits to London. Residents/regular commuters who are thoroughly familiar with their usual stations and stops might not be interested and wouldn't learn much.