MTA reportedly had planned versions for Android and Windows users, but on Friday noted those options would be advanced by third-party developers.
The app is available to riders of the 1,2, and 3 lines on Manhattan's West Side, the 4, 5, and 6 lines on the East Side, and the Times Square shuttle linking Times Square and Grand Central Terminal.
Comparable service is expected next on the No. 7 line, now having Communications-based Traffic Control (CBTC) installed, and on MTA New York City Transit's L line, which already has CBTC in operation. The L line may be upgraded in 2013.