The Go-Yo Lanterns were handheld mutant detectors. When facing a person, the display on the back showed baseline Humans as a dull green colour, but Mutants as bright red. This allowed the police to identify mutants even when they weren't using their powers and apprehend them.
Notes
As with many things of Earth-2301, the Go-Yo lantern is a mix of Western and Eastern aesthetics, resembling the lanterns associated with the antiquated police forces of both Japan and Victorian England.
