The MTA has been making real-time subway information available to developers for a couple years. However, one must contend with the GTFS Realtime format, which isn’t as easy as digesting an API. This is especially true when one only wants the status at one or two stations.
Enter MTA Sanitizer, Jon Thornton’s JSON proxy for real time MTA subway information. This looks like a very promising project for those looking to get at the real-time information. It needs to run on a server somewhere, but everybody has one of those.
I really wish this was available when I was trying to include real-time subway information in my Good Morning Display.