What does NYC Exit Strategy do that standard subway map apps don't? Tells you precisely which subway car to ride in so you get off exactly where you want to, as close to the right exit as possible.
Just pick the line, your stop, and whether you're going uptown or downtown. (Yes, it works offline, since there's no AT&T in the subway, or anywhere in NYC it seems at times.) It shows which subway car is closest to which exit. Like say if you're going to Union Square and want to get off at the 16th St. end, not 14th by the carcass of the Virgin Megastore. Used every time you're on the subway for a year, the hour of time you save not wandering from one end of the subway station to another to get out where you need to easily adds up to $2.