Where in the world will the wedding box unlatch?

There’s only one spot on Earth to open this wedding gift.

It comes in a small, carved wooden box -- equipped with a GPS circuit -- that won’t unlatch until it’s taken to a preset, mystery location.

And the recipient has to figure out where that is.

It sounds like something from “Mission: Impossible” or a James Bond movie, but this is a real gift made by software engineer Mikal Hart for a friend who was getting married and moving to France. And it has to be one of the most mysterious, geeky and delightful wedding presents of the year.

“I’ve always been fascinated with puzzle solving, and I thought something fun could be done with GPS,” said Hart, 46, who works for Intel Corp. in Austin, Texas.

He bought the box, festooned with a carved elephant, at a World Market store and mounted a little digital screen, push button and GPS chip on the lid. Inside went the rest of the electronics and a little motor for the latch.

The box was delivered with no instructions. When the button is pushed, a message comes on the screen giving a distance in kilometers. It also shows the number of times the button has been pushed -- the maximum allowed is 50.

Hart hopes his friend, who received the box last month, will figure out that the distance on the screen is a GPS-derived calculation of how far he is from the target spot in France. With three clear readings, he could triangulate to find the goal.

Here’s hoping he’s not reading this: It’s the island of Brehat, a destination spot off the coast of Brittany where the couple met. Upon arrival, the motor will automatically turn on to free the latch.

“What would be better than to get in a boat and go to the island to open the box?” Hart said.

The contents had to be small to fit in the box -- they’re mostly gift cards. But if it’s the thought that counts, this one is priceless.

“It took me nine months, off and on, to figure it out and build it,” Hart said.

As people discover his website, at arduiniana.org/projects/the-reverse-geo-cache-puzzle , Hart is getting requests for boxes.

“I was set up to make only one,” he said, “but people are asking.”

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david.colker@latimes.com