I have not had great experiences with Hipmunk online so I would be a little weary of their app, but that is just my personal experience and I am sure that everyone is different when it comes to that. I am pretty sure that all of those big sites like Expedia and Tavelocity have their own apps, and I am assuming that they are tailored to do many of the things that you can get on their sites but just more convenient. I would say poke around and see which one suits you best.