Remember the 802.11n Wi-Fi adaptor for the Xbox 360, which appeared in an FCC filing in the States back in September? Well, it appears that it's real and it's on shelves in Asda, if the above picture from Engadget is accurate.
The pic puts the price at £50, slightly less than the current b/g version which costs £60 (though can often be found cheaper than that). The product can't be found online from any of the big supermarket retailers, though, so it seems like this could be just the work of an enthusiastic shelf-stocker.
The peripheral enables the console to connect to faster, more stable Wi-Fi networks, which should improve your online experience if you suffer from a slightly dodgy wireless experience on your console. For it to work, however, you'll also need a Wireless-N router - something that isn't yet in many people's homes.
We'll keep you posted of the wider availability of the device. If supermarkets are getting stock then that could be very close indeed.