Made this as a wedding gift for my sister and her husband... it works like a compass, but instead of pointing due north, it always points towards the park where they got engaged (Tompkins Square dog park in NYC). The box is powered by an Arduino, a GPS receiver, and a digital compass, which drive a servo motor that moves the compass needle. Code is adapted from Instructables user r10n here: http://www.instructables.com/id/Steampunk-Geoca... )
NOTE: the box is not super accurate to begin with (only gives a loose sense of direction), but is particularly off in this video. I think it's because I shot it on a kitchen counter, and the drawer of silverware underneath it was throwing off the compass.