I’m always amazed by the sheer ingenuity some people have for making things out of scratch, and this case is certainly something that falls into that category.
Here’s a nifty little case made by Arduino Forum member RickP, that can only be unlocked when it is at the correct GPS coordinates that have been programmed onto the case. He uses an Arduino, a GPS sensor, and a trio of nixie tubes, which indicate the box’s distance from that special spot. When the button is pressed in that spot, a servo motor unlatches the lid.
As the nixie tubes draw a lot of power, Rick has powered the case with 4 D-cell batteries and estimates that the case can do 600 GPS fixes before they run out. The power to the case is connected by a latching relay, which allows the Arduino to shut the power off after the GPS fix has been attained and distance has been displayed.
Rick refers to the case as a reverse geocache (because that is just what it is) and it is made out of a metal medical box from the French army and Ikea door handles.
As interesting as the case is, I have to say I do express some doubts as to being able to bring the case along on a trip, especially onto a flight. Personally, I just loved that he used nixie tubes in the design, as I’ve always been fascinated by those home-made nixie tube clocks.