While there are now a few different companies that build self-balancing one-wheeled electric skateboards, Future Motion was one of the very first. The California-based firm has just announced the latest addition to its lineup, the small but mighty Pint S.
I sold mine a while ago after moving, but when I lived in Portland I put almost 800 miles on it commuting to and from the max station. They are easily the coolest way to get yourself killed out there.