The easiest way to detect nuclear material is typically when it's already too late. By the time seismographs, infrasound sensors, and radiation readers pick up on a blast, it's already happened. Catching a nuclear weapon before it goes off is a lot trickier, which might be why the Department of Homeland Security (DHS) is looking at some rather unconventional ideas. The latest: a small, wearable radiation detector. Think of it like a FitBit, only instead of telling its user about calories burned, it lets them know if they're close to any nuclear weapons.

Huban Gowadia, Director of the DHS's Domestic Nuclear Detection office, last Thursday blogged that the Department has awarded a multimillion dollar contract to develop such a device. The DHS is calling it the "Human Portable Tripwire." She writes:

The award is for small, wearable radiation detector devices that passively monitor the environment and alert the user when nuclear or other radioactive material is present. Known as the Human Portable Tripwire (HPT), this device has the capability to identify the source of radiation and allow personnel to take appropriate action. The technology can also locate the source of the detected radiation and includes communication features that allow the user to easily seek additional technical assistance from experts if needed. These devices are a critical tool for personnel who operate in the maritime environment, at land and sea ports of entry, and within the United States.

The device will be used by the Coast Guard, U.S. Customs and Border Protection, and the TSA. The project has been in the works for a while; the DHS posted the first notice of the contract in June 2014.