That device is already here. Although it is not a radar, it provides a similar result. It is called the Weapon Heat Sensors. It is an innovative invention that will save lives. Lives like yours.

With Weapon Heat Sensors, you can reveal heat emitting objects behind obstacles such as walls, doors, boulders, trees to name a few using a FLIR infrared thermal detector. As an added feature, our one-of-a-kind unit is also enhanced with two long range metal detecting capabilities that can recognize carbon steel, stainless steel, iron, and aluminum weapons. A size of a dime, the metal detectors are a necessity when combined with the FLIR Infrared detector in detecting assailants in ambushed scenarios where the Fog of war is the most unpredictable.
In these uncertain times, the market for personal early warning devices is at its infancy. There aren’t a lot of these types of devices sold in the

Global arms market. So, there is plenty of room to expand and one of these niches is in the field of Security such as the Police department and the Military. As for its uses, besides in a combat situation, the Weapon Heat Sensors is fully capable in search and rescue of missing persons, as well as detecting fugitives in hideouts.