Developers have sometimes asked what apps should do if edge gestures are accidentally invoked, especially for time-sensitive games.
For top/bottom swipes, these will invoke your own app bar if you provide one (otherwise they have no effect). In this case you can use the beforeShow/beforeHide (WinJS) or Opened/Closed (XAML) events to know when this happens.
More fundamentally, you can also use the events in Windows.UI.Input.EdgeGesture to detect the top/bottom swipes but this is a somewhat lower-level mechanism.
If you haven't seen it, the Designing great games for Windows topic in the docs is also worth a read on many other important points.