Back in 2011, Google added the ability to keep up with live transit updates to Google Maps. After all, commuters in big cities that require cars to get around (like my own Atlanta), have traffic info for highways. Why not people who primarily use the subway to get around? One glaring omission from that service, though, was the New York City subway system. Today, that problem is rectified.
Starting today, seven lines of the MTA will show live arrival and departure times for stops along their routes. Additionally, public transit users in Salt Lake City can get the same information for buses and trams in their area. Also, the Metrorail in DC now shows service alerts when, for example, there's scheduled work being done on the tracks.
The information is available on Google Maps via the desktop and Android apps.