I'm not sure that it's as clear cut as doing something that can't be easily copied — any iPhone app that stores data locally is vulnerable to this. (In fact, I'd advise other iPhone developers reading this to have a close look at any suspicious competitors). I'm cool with someone 'stealing the idea', just not when they go selling my implementation of it.
All that said, if you really feel that this is something that you want to do something about in the future, apps like 1password encrypt local data. I haven't done it, and other people have said it's a PITA because documentation is lacking... so YMMV. But, think of it this way, put that anger into learning how to encrypt/decrypt things on the iPhone. You'll gain a great skill while at the same time getting to code a project that allows you to mutter, "Let's see that stupid muppet steal THIS data..."
* Did I really mention that I like the word muppet? :D
But I feel for you. I definitely think you should tell/threaten to tell his school if he doesn't take it off the app store.
What can you do with your app that isn't so easily stolen (and reproduced) and turned into a carbon copy? As you've already seen, public transit apps are a dime a dozen. How about a bigger/better itinerary application that includes trains, planes, and automobile times so that one can put an itinerary together of vacation travel across all of Ireland? Add hotel info, confirmation info, etc, etc, etc...
I don't have the links handy put there have been other articles on HN about lessons from stolen work. Big lesson: it rarely matters because the people stealing ideas and work don't have the skillset to do it themselves. In the long term they can't compete with the new features and directions that you'll go.
What I'm trying to say is, use that energy from your anger to create something fcking awesome that that stupid muppet won't be able to compete with.
* I'm from the US. Yesterday, I learned about the use of the word muppet over on that side of the pond. BRILLIANT!