Taken directly from this article.
Nintendo is now including the Wii Remote Jacket for the Wii Remotes in all new hardware being shipped. For Wii owners who purchased their systems prior to this addition, we are offering to send free Wii Remote Jackets for their existing Wii Remotes. If you would like to request a Wii Remote Jacket, please start by completing the information form below.
If you have already submitted a request and want to check on the status of your order, please click here.
Please note, we will begin shipping Wii Remote Jackets on October 15th, 2007. Once your Wii Remote Jacket has shipped, you will receive a confirmation email from Nintendo. After that point, it may still take another 5 to 10 days for delivery depending on your location. Please do not contact Nintendo regarding your Wii Remote Jacket order until after that time period has passed.