It was a totally random science project, but it ended up taking about 15 hours total between last weekend and this. It is CoasterBuzz for Windows Phone.
Basically, I opened up a service on the server, wrote some junk for the phone to consume it, and opened access to the park and coaster databases from the phone. For the most part, I stuck to the design guidelines and didn't try to get too fancy. Much of the time spent was just trying to understand some of the navigation weirdness and maintaining state.
If it gets any real attention once it's live in the marketplace, I'll consider adding some features. Right now, it's just something I wanted to prove to myself I could do in as little time possible. Hooray for iterating quickly!