InterAct Accessories is a game peripheral manufacturer founded in 1991. They created controllers for several game systems, and they created the original GameShark cheat devices.
InterAct was a company that first released the GameShark line of cheating devices for various platforms. It's parent company, Recoton, went bankrupt and InterAct is now defunct.
InterAct acquired the rights to sell Datel's Action Replay and Pro Action Replay devices in North America; these devices were sold under the GameShark and GameShark Pro names. InterAct released GameShark devices for the Game Boy, Game Boy Color, Game Boy Advance, PlayStation, PlayStation 2, Saturn, Dreamcast and Nintendo 64.
Source: Wikipedia, "GameShark", available under the CC-BY-SA License.