Scouter (Dragon Ball)

The scouter was a device invented by the Tuffles that consisted of an earpiece and a lens over one eye (the lenses came in three main colors: red, green, and blue). Its purpose was to "scout" an enemy and determine their battle power. After the Tuffles were wiped out by the Saiyans, the Saiyans adopted the use of the scouter. After joining with Frieza, the Saiyans shared the technology, and thus all Frieza's warriors came to wear scouters.

It should be noted that the members of the Ginyu Force and Cooler's Armored Squadron, as well as the warriors serving directly under King Cold, all wore scouters that were more advanced than the "basic" scouter and were smoother in design.