Now when there are less then 2 months wait for the new iPhone, (my bet is October 5th) I have two apps to recommend.
There are a thousand travellers apps out there. I have tried many of them but these two are the ones that I use by far the most. The Copenhagen airport app is quite good when you are travelling yourself but also good when you are picking somebody up at the airport. You just subscribe to the flight and get all updates and even a notification when they start to load the bags on the belt. It has quite a few bugs but overall it works.
The other one is the Currency app. It is so simple and just continuously being used.