IPhone app for NYC transportation?

I'm going to NYC soon and I wonder if there's an iPhone app that's able to tell me what to do (I mean buses or metro or both) having only my location and my destination.

My friend, you can go to the website of the Metropolitan Transportation Authority, which is the transit agency in charge of the city's subway, bus and commuter rail network, and download a free map of the city subway system to your phone. Its free.

I'm a long time New Yorker and I also have an iPhone.

I use 2 apps pretty regularly.

Hopstop will give you step by step directions as to the best route to take by any mode of transit in the city. It is always updated about service changes.

Also I use itrans NYC which is just an app with a subway map, but it includes up to date service alerts.

Remember though, most of the subway system does not have internet access yet.