[Woeps]

Uhm, Don't most underground trains already show you where you are? Or at worst, the sign of the station shows you your location?

[yaky]

I think it's one of the "pointless but cool" projects, but yes, I don't get it either. Any decent underground system would already have audio and visual announcements; I don't think I have ever cared to know where between stations the train is.

[makeworld]

Supporting it in the app allows connection info (bus, other train, etc) to be updated and to warn the user if they'll be late.