An application that shows you if your train will be late, and that in real-time! Even better, imagine that bundled with an API that gives you access to all that data. So happened in Germany with the application Zugmonitor (German for train monitor) and the corresponding Zugmonitor API.
For a series of articles about delays in the German railway traffic, newspaper Süddeutsche has contracted company OpenDataCity to build Zugmonitor. OpenDataCity has specialized in applications with a focus on data journalism, frequently making use of large data sets. It speaks for the company, that they quite frankly admit that to make Zugmonitor possible, they had to scrape the data from the website of Deutsche Bahn (the German Railways).
Zugmonitor shows a real-time map of all trains in Germany, their current position and status. The trains, represented by arrows, are overlayed with differently colored circles, indicating an estimation of the current delay of the respective train. When clicking on one of the trains, the train's route and the reasons for the delay are displayed. Another interesting feature is the playback functionality, which lets you revisit how the train delays have build up over the course of the day.
Zugmonitor gets its data from the Zugmonitor API. It provides access to all train station names, and the status of a train on a specified day. The API can be used for non commercial applications only, probably due to the nature of the data acquisition by OpenDataCity mentioned earlier.
One final thought from a German: We Germans are know for our punctuality, so I think it is quite fitting that with Zugmonitor we now have an application for the delays in our railway system.