Well, it connects to a smartphone to provide the user interface. There's a small single-board computer that runs inside the device and does all the heavy lifting for computation.
Law enforcement personnel will wear this system. They will often be doing this in a plainclothes scenario. When there's a large event with a crowd of people, for instance, they can easily walk through and amongst the crowd, and the system is constantly looking for any indications of elevated radiation levels. Importantly, it also is able to discriminate between different types of radiation. You can have many innocent or legitimate sources of radiation, like people who have had a nuclear medical procedure. It can differentiate between that type of radiation and the type of radiation that might be associated with a weapon.
It's one example of many different types of products that are used by law enforcement that use mobile systems, airborne systems, and systems that are mounted on maritime vessels. The goal is simply to try to increase the probability of detection of illicit materials, preferably before they can be assembled into any kind of a threat, and be able to then intercept those materials before anyone can deploy them.
In the United States, for example, after 9/11 there was a recognition that threats such as nuclear threats, as well as chemical and biological attacks, were things that law enforcement needed to be concerned about. In the intervening years, there has been a heavy investment to equip regular law enforcement agencies with this type of equipment so that they can assist with carrying out that type of detection mission.