Have you considered encrypting your database, so that only your app can make sense of it? That's what a friend of mine used to do, and it indeed stopped some superficial copying.
With the added benefit of bring able to tell when someone else accesses your content by failing to supply a special request header.
I would start by trying to talk to him. If that didn't work, I would call his school and make them aware of their student's shady doings. Then I would go to Apple and point out Apple is helping this guy to infringe on your copyright (the database is comprised of public data, but your work compiling it is non-trivial).
If the data were kept on-line and cached in the client, you could, as a final step of escalation, render his app useless. Or worse: make it supply wrong routes.
But he can do the same thing to you.
In the end, the users win. That's the beauty of a platform that has critical mass in numbers of developers competing to make good apps. Sucks for you (us) unless you look at it as a fun challenge.