Even though the Twin Cities only has one LRT line, it already has an iPhone app to tell you where the nearest station is and when the next train is coming. Train Brain was developed by Andy Atkinson and sells for $1.99 on iTunes store. Minnpost has a write up on the application and the summary of an interview with Andy. I concur with the author, Metro Transit should buy this application, or maybe better, hire Andy to build a full system app.
To be fair, Metro Transit has it’s own trip planning tool, NexTrip, that is accessible with an iPhone or other mobile device. But it is not location- or time-aware. The first thing you have to do is scroll through hundreds of routes to find yours, not easy or quick on a mobile device.