"Wheel skates" are roller blade style boot with bike sized pneumatic tires for a "smoother, more fluid skating experience that crosses boundaries into skiing and cycling" with carbon fiber construction and optional hand brakes.
The inventor, Michael Jenkins, claims "I usually overtake recreational cyclist[s]" as he travels at 20 km/hr, but then don't we pass pro cyclists while riding old 12" kid's tricycle all the time? Chariot Skates hope to launch these for sale next February, 2010.
They do look very fast. I wonder if they mechanically permit the speed skater position, or if you are always bolt upright like shown. Like someone (BikesnobNYC maybe) mentioned, skaters take up a room laterally. You can see that when two of them are trying to skate side by side, they can just manage it. But it doesn't look like these take any more room than inline skates, anyway. I, too, would totally break my neck the first day out. On that second day, though, with the neck brace on, I would fly.