Riding a unicycle without the faceplant.
Nick Thatcher built this self-balancing unicycle using an Arduino UNO, a IMU (gyroscope) from Sparkfun, a 24v 350w geared motor, a wheelbarrow wheel, and a handful of other basic parts.
The IMU senses when the unicycle tilts too far forward or backward, the Arduino does some calculations, and then the motor compensates. The rider still has to put a little effort into maintaining balance (and not falling sideways), but it wouldn’t be much fun if the Arduino did all the work.
Via Hack a Day