Station Master (US$3.99) for iPhone and iPad has all the information you'd ever need to know about every station on London's Underground, Overground and Docklands Light Railway network. If you live in London, are planning a trip to London, or you simply have a fascination with London's trains and stations, the app has a wealth of knowledge to help you better understand and travel the network.
The recently updated app, co-created by Geoff Marshall, the Guinness World Record Holder for traveling to all tube stations in the fastest time possible, now features 3D maps of all 270 stations, so you can see every stations layout in its entirety. Other app features include Exit information, Accessibility information, station facilities (WiFi, toilets, shops etc), transport links from stations (buses, National Rail, cycle hire) and travel tips, tidbits and station history facts.
My favorite feature is Exit Information, which shows exactly which train carriage and door to exit a train from, so you can make the fastest exit from a platform via passageway, lift or corridor. It's a glorious feeling when you exit a train and walk straight through to the platform exit, avoiding the hustle and bustle of fellow commuters and tourists trying to find their way. Another great feature is the apps info on station accessibility, with details on lift availability, measurements of gaps between train and platform, and even stair counts.
One thing to note is that Station Master is not a route planner, but rather a tool to navigate the stations you use when traveling London's railways. As a side note, the app developers run an interesting blog on all things London-train / app related. It's worth checking out.