First I would get some basic idea of what your application needs to conform to in order for it to pass as a valid project. Only then I would worry about an actual idea.
Example: I had to do such a project and my project group initially took the easy way out by wanting to build a webshop. It turned out that this was not allowed because it would be far to easy to download something off the internet and use that.
My advice is to not try and be innovative, you want to pass your project, not become the next dot com genius. Make something that exists already so you have something to "be inspired by" (as in steal ideas from). So to get your idea: go surf around the net until you spot something that you think you might be able to do.