FLIO, the sort of Swiss-Army-knife utility for getting through and around airports, has now reached a million users, and keeps on adding features. We've covered FLiO before, and it remains a top choice for reducing airport stress.
The award-winning app, with Android and iOS versions, aggregates a wide variety of useful-in-the-airport tools, including finding and logging into airport free WiFi at hundreds of airports. It also uses GPS and its vast database to find you the nearest bathroom, power receptacles, shortcuts to your gate and more, as well as sending you notifications of gate and flight changes. It claims to be the fastest at that.
It can also directly book services in the airport or transportation from the airport, such as Heathrow Express, as well as lead you to discounts at airport shops and services it has signed up.