The Waikiki is believed to be a debugging device made by Nintendo. This is the official version of what became a USB Gecko from the homebrew community, which later was recreated by someone to make what they called a Shuriken USB. Waikiki is named after a neighborhood in Honolulu, Hawaii, possibly due to the high presence of Dolphins there.
The Waikiki dongle was used during internal "lab testing", as well as factory initialization, of the Wii and possibly the GameCube. RVL_DIAG contains a program used to test the Waikiki's operations.