Its a great app to have, you can see the delays and changes which helps in avoiding any inconvenience. It also lists stops on each line. I use the nearby function and find it very useful to know what time the trains are arriving. It used to be off by a minute of more but its been great for the last few months. Plus you have the subway map, which allows you to select each stop and check the timing there as well.
mi5t4ak about NextStop - NYC Subway