Wii Speak is coming your way on the 16th of Nov, well if you live in the US anyway.

It launches at the same time as Animal Crossing: City Folk and Nintendo had this to say -

 " The new voice chat function makes use of the new Wii Speak accessory, a microphone that sits on top of the television and allows entire rooms of people to communicate with one another. Only users who have traded Friend Codes can connect with one another using Wii Speak. The accessory is sold separately at an MSRP of $29.99 and will also be available as a bundle with Animal Crossing: City Folk at select retailers at an MSRP of $69.99. The Wii Speak accessory comes with a code that lets users download the Wii Speak Channel from the Wii Shop Channel at no charge. "

Source