This would be so awesome! What would you want to do with this?

Dunno, could see someone writing an app that you would register your daily commute with and maybe it texts you if there's a disruption.

Someone else could write a system wide eye-candy visualization of where all the trains are.

Maybe I could have it detect when the F train is 10 mins from my stop and ring an alarm on my phone so I know to leave my apartment in morning.

Or have it wake me 45 mins before the train closest to but not after 8:30, so I'm not late for work cause I just missed a train, and I'm not standing on a hot crowded platform for 15 mins.

Think about riding the G train again. Could be possible with this information.

Not sure what the resolution of data the MTA has about the positions of their trains and buses though.

It's not a traditional REST API, but you can download all of this data in GTFS format from the MTA's website - http://mta.info/developers/download.html

So I think the killer app is: I'm in brooklyn at a party it's 11pm I want to know where the G train is? Should I leave the party now or have another pabst blue ribbon cause the G train is in staten island moving at 2 miles per hour and won't be at Metropolitan Ave until next tuesday?

Schedules are less fun than something more realtime. The MTA must have some tracking, I've see old school tracking boards that lightup as trains roll over switches. Plug an arduino into that and broadcast it out over REST.

@Kyri I agree -- I think something like that would be amazing, and is likely feasible from a technical perspective, but who knows why the MTA doesn't already do this..

The MTA already has real-time at 1/3 of the stations. Problem is that data isn't available to developers yet. See mta.info link above. But a good alternative for now is the Roadify app, they won Big Apps this year. They combine schedules with real-time user reports for buses and subways.

Check them out here: Have you checked out this year's Big Apps Grand Prize winner, ROADIFY? They combine bus schedules with real-time user reports about bus locations. I know they often reward their top users with prizes like metrocards and stuff.

Check them out here: http://itunes.apple.com/us/app/roadify-nyc-commuting-parking/id395111132?mt=8

I think that this is probably much more feasible for the subway lines that already have the timing data such as the L and the 4/5/6 but I would love to see data like this open to everyone. Sadly Roadify only works with buses, and not subways.

Relatively precise location data is only available for the L-Train and all of the numbered (IRT) lines, except the 7-train. It is also available on three bus lines (M16, M34, and B63). See an example here: http://bustime.mta.info/

As far as I know the real-time data for the subway lines that have it is not in the API yet.

To Kyri's point above: "Plug an arduino into that and broadcast it out over REST."

The MTA has started doing this for their B Division (lettered lines) other than the L:
http://secondavenuesagas.com/2010/02/17/along-the-b-division-a-cheaper-countdown-clock/

I'm actually working on something like what Kyri has described right now. The problem is that it only relies on timetable data, rather than actual real time stuff which as Brian has said, isn't publicly available.

That said, the timetables are surprisingly accurate.

Correction to @John P's point, Roadify does subways, buses, and parking info as well. I like them alot b/c I dont need to check 3 apps everyday, ya know? Have you checked it out John?

@Alastair, what kind of project are you working on?

Great idea but the city of NY does not control MTA data