spy++

Is there a Qt widget to browse the hierarchy of widgets in an app (similar to Spy++)?

We've got an app with a complex hierarchy of widgets and I want to be able to browse this hierarchy, view and edit properties (such as size) in a similar manner to Spy++. It doesn't need to be running in an external app, if there is a widget that can display this information. So the question is, does such a mythical beast exist? ...