Buy Endless Ocean: Blue World from Amazon and you get Wii Speak as a bonus. Amazon’s product page says “One Wii Speak microphone will come bundled in the box with a limited number of Endless Ocean 2: Blue World orders.”
Endless Ocean: Blue World uses the USB microphone for in game chat when you dive online in the game’s co-op multiplayer mode.
Amazon sells the Wii Speak microphone alone for $25. If you were thinking about buying Wii Speak for The Conduit you can get Endless Ocean: Blue World for an extra $5. Interestingly, Gamestop does not mention a Wii Speak / Endless Ocean: Blue World on their product page.
A tip of the hat to Andy for the tip!