If you live in the D.C. area, there are quite a few mobile apps that show next train arrivals for the D.C. public transportation system. We've got a better way to jump straight to the info you need to know without the fuss of opening an app or navigating through a website interface.
The Washington Metropolitan Area Transport Authority (WMATA) in charge of the DC/MD/VA metro system has a great mobile version of their website's next train arrival tool. On your smartphone if you wander over to wmata.com you're given a bevy of options.
Focusing on next train arrivals, select your station (through an odd navigation choice of alphabetical groupings of stations) and you're presented with all the train info for that station. You get the line, direction, and number of cars on that train.
For our tip we used an iPhone and selected the option to add this website to the home screen. I took it a bit further and created a quick folder with all my travel related links. You can see I've got shortcuts to the two stations I use for getting between home and work. The web browser conveniently refreshes each time I click the shortcut to load the page, or I just tap the refresh button. Sitting right on my home screen, it's a quick and direct way to get to the information I need in as few steps as possible.