This guy built his own 1-axis-balancing (forward/backward) electric unicycle.
THIS is a cool toy, and I want one.
His website is here and has more videos.
Another guy has built a similar one and has all the specs available. The total cost for materials is about $1500. However, that one doesn't have foot-turning like the Enicycle (you turn it like you would a unicycle, eg, arm-flailing).
There's got to be a way to make one of these that is 2-axis-balancing...