The Reverse Geocache. Box only opens at one spot on Earth.

A single button on a wooden box. Press it and a digital display reads "Hello, This is attempt 1 of 50" The message is suddenly replaced by a new one: "Access Denied". A third message give the only clue as to how to open the box: "Distance 257 miles".

Despite being subjected to the old box in a box in a box birthday gag repeatedly as a kid, I love when the delivery of a present is filled with mystery. It doesn't get much more mysterious than this.

There's a great write up on the spirit of this project over at Arduino artist Mikal Hart's Arduinia Website.

Thanks @seanhaus