The Self-Balancing Unicycle (or SBU) by Focus Designs incorporates the same kind of technology that keeps the goofy Segway upright. It uses accelerometers and gyroscopes that allow the SBU to know which way is up and which way you're leaning. That's how you control the SBU actually — the pedals are just for show.
From Focus Designs:
The rider controls the speed by leaning forward or backward to speed up or stop. There is no need to pedal, in fact there are no crank arms, just foot rests. The SBU keeps upright by utilizing advanced electronics including accelerometers and gyroscopes with sophisticated balancing algorithms. It's truly an experience like no other.
Before you think your balancing woes are over, take a look at the price of the SBU: $1,500. Still, if you're that clumsy, it'll be cheaper than a bunch of broken bones.