First, B&N filed trademark for "Nook Audio" back in February. I didn't post about it at the time because B&N was going through a phase where they trademarked everything (I think there was even a trademark for "Nook Kitchen Sink"). I didn't know which of the terms would be used, so I decided to wait and see what happened.
Also, Barnes & Noble hasn't passed any new devices through the FCC, and the lack of FCC paperwork indicates that it won't be a Wifi equipped device such as an ereader or mp3 player.
But I'm posting about it today because now I have the product page. There's hardly any info on it, but the fact it is there tells me that the product is coming. We also now have a model number, OE250, and that tells us a couple things.
The model number is different from any of the Nooks, so this likely isn't a Nook with sound. It's probably not even an mp3 player; B&N would probably have built Wifi in and had it run Android (it would have been a mini Nook Color).
So what we have here is an audio accessory. The Nook Touch doesn't have sound, so this would have to be for the NC or NT. It might be as boring as headphones, but I'm hoping for a stereo dock. A couple different companies have them in the works for the KF and Nook Color (here, here), so there's a good chance that B&N also thought now would be a good time to offer one.