I think it needs a little more ergonomic design work, but Honda's U3-X looks like it could be useful in at least a limited set of circumstances. Coolest feature: an omnidirectional wheel.
The single wheel on the U3-X — U stands for "unicycle" and "universal" — is made up of many tiny motor-controlled wheels, packed inside the bigger wheel, allowing the device to swerve in any direction.
