Developed by researchers at the University of Southampton in England who were intrigued at how dolphins were still able to pinpoint fish they were hunting even in the middle of distracting clouds of underwater bubbles, the TWIPR—or twin inverted pulse radar—borrows techniques from the ocean's smartest inhabitants.
Namely, a technique where two signal pulses are sent out instead of one. This approach allows dolphins to distinguish between fish and bubbles, but with the TWIPR technology it can be used to detect electronics. When the pair of positive and negative pulses hit something like a tree, a rock, or even metal, they cancel each other out and disappear. But when the pulses hit a device made with semiconductors, the negative pulse becomes positive, doubling the signal and making the electronics very easy to spot.
What's particularly awesome is that the new technology—which could easily find a bomb hidden in a dumpster full of trash—measures just two inches in size and can be built from electronics costing less than a dollar. So putting it into production and into the hands of those in danger shouldn't require much further development. More here.