I used a pair of old sunglasses as suggested – works perfect!
Just tested it in Google Earth for 20 minutes or so and it is very usable. Not quite as accurate as using 4 PS Eye cameras but still very good. I am experimenting now with the placement of the Kinect in the room to see if I can improve it.
Another user mentioned using 2 Kinects to average tracking data like PSMoveServiceSteamVRBridge does – if this is possible, that would be perfect for 360 degree/room scale tracking!
Also I should mention my CPU is quite old (i7 2600) and is still doing fine.