This is a ziploc style bag designed especially to protect iPads. I guess it could be used on Kindles and other ebook readers. I often use a ziploc bag to protect my gadgets so I'll be trying these as soon as I can get my hands on one.
The Chef Sleeve is currently featured on
www.ipadforums.net
There's a video demonstrating it. The first three minutes of the video are boring but then it gets really amusing.