I have developed a flight-controller for the BGE with Python and Leap Motion. The user controls the orientation of the camera and the direction of the movement of the camera by the motion of his hand. Here you can see a flight through the historic centre of Landshut (Germany):
I didnt’t model this scene, I just downloaded it from Open Street View: http://wiki.openstreetmap.org/wiki/3D_Development
The blender file in the attachement contains the flight-controller but not the city.
leap-motion-flightcontroller.blend (610 KB)