Imagineer Russ Nelson has taken it upon himself to improve the keyboard, a device that hasn't seen any real innovations for ages, seemingly. His Mark line of keyboards, the latest being the Mark VIII, are designed to be used with just one hand. Considering much of it is made out of cardboard, the low weight shouldn't surprise anyone.
The Mark VIII is designed in such a way that there's no support base underneath the palm—all weight, as little as there is, is pushed against the thumb. This leaves the other four fingers free to type. As you can imagine, his design went a couple of revisions before his latests, which is currently just lacking CPU code, which he calls "the easy part."
Practical? Debatable. Übernerd cool? Even money.