I found this posting on Sideshow Devices for a Windows Sideshow device that is an eInk based eReader intended for the home.
It's a concept demo made by a company called Ricavision that seems to be working with (or leveraging the names and marketing dollars of) Microsoft and Intel.
Here is a link to a PDF Press Release of it.
The gist of it is that it's an eInk display eReader device with wireless (Wi-Fi) connectivity back to the PC running Windows Vista. It's configured on the PC as a sideshow device and hence it can act as a display for the Windows machine, content to view can be pushed to it (and cached) and it seems it can also control to some extent the Windows PC (from the Sofa?).
As small and lightweight as a single book, the Ricavision Home E-Reader allows users to download and take along newspapers, books, and documents, or upload them to share with family, friends, or co-workers.
In addition, the stylus capability enables the user to make notes that can be easily transferred to a PC and then transmitted to others. If desired, friends or colleagues can add their own comments or edits and return the notes to the original user."
Not sure I 'get' the big advantage of this over an un-tethered eBook that connects back by USB to the PC.
I suspect the big advantage is that if you do it like this, using the new SideShow functionality from the newly introduced Windows Vista - then you can count on a lot of visibility, a few references in Bill Gates' keynotes, and a pile of Microsoft Marketing cash to help get your start-up's product into the press and the blogs (like this one).