Tokyo Metro released a new Android app recently. It is good to see more companies doing this. The app is surprisingly complete and includes station area maps, diagrams of station interiors, exit information, elevator/escalator/barrier free information, station list for each line, transit search (for metro only), and GPS functionality. I think that covers it, though I could be forgetting something. It also big, 11 MB
The list of stations for each line is well thought out and allows you to click through to the station information pages. It doesn't support landscape rotation, though, which makes displaying station interior diagrams a bit awkward. There is no English localization.
To view detailed information for each station, click on the station in the line overview map (you'll want to click the button on the left to dismiss further messages).
Size: 11 MB
Requirements: Android 2.1+
Click a station to display detailed information.
From top: Station interior diagram, exit information and area map, "barrier free" information, Marunouchi line station list.
Hopefully the next version will support landscape.
Barrier free information.
List of stations is clickable.
Transit is for Metro lines only.