Your tax dollars at work...
The Defense Advanced Research Projects Agency, which in the past has funded such experimental projects as ARPAnet (an experimental computer network that was later renamed the Internet) is currently funding a project called the "Self-Healing Mine Field."
The basic premise is this: An army lays down a field of antitank mines. The mines all communicate with each other, and have the ability to move. If someone clears a path through the minefield, the mines react by automatically rearranging themselves so the path is closed.
And you though people had trouble clearing out minefields left behind from long-forgotten wars now.
There's a Flash animation about the project that you have to see to believe here.