Antoine Triplett retrieved his grandfather's Howling Commando gear and offered it to Phil Coulson as a tactical advantage during the undercover investigation on Cybertek and the missions to come. The EMP Joy Buzzer was among these items and Skye, not knowing its function, used it unconsciously to destroy the light bulbs inside the motel's room.
Leo Fitz took advantage of the innocent appearance of the device when Grant Ward abducted him and Jemma Simmons in Cuba. As they were taken to John Garrett's presence inside the Bus, Fitz used the device against Garrett, damaging his cybernetic prosthesis and bringing him to the brink of death.
The EMP Joy Buzzer creates an electromagnetic pulse that has a 10ft range radius. As with all EMPs, the pulse disrupts all electrical applications within its range. Although the buzzer was made in the 1940's, it was powerful enough to disrupt Garrett's cybernetics which were made in the nineties.