What should the military do when GPS goes down? That's a question DARPA has spent a lot of time and money on, and Danger Room just got an in-depth look at the answer. It's a tiny chip about one third the size of a penny that contains gyroscopes, accelerometers and a master clock — dubbed Time and Inertial Measurement Unit or "TIMU." Together, that's enough to produce an airtight record of your movements, which will keep your coordinates accurate until you can get your GPS connection working again. It's useful for soldiers, but crucial for the bombs, missiles and gliders that rely on the system.

As the piece points out, the military has very specific reasons to be worried about this right now. It's relatively easy to jam or spoof a GPS satellites, and many states may already have the capacity to do so — most notably, North Korea. Of course, the ideal solution would be to strengthen the GPS system, which is still the first priority. But in the event it fails, DARPA will have TIMU to pick up the slack.