A picture of the Ryno is to the right. (I have yet to see one in the wild). It is self-balancing, and so the Segway of mobility scooters/motorcycles. As they say, don't let the road get in the way of your life. It is limited to 12.5 mph, and so one may ask, how is this better than a bicycle? Well if you don't want to pedal. ... How is this better than Segway? Well if you don't want to stand, and somehow it looks cooler.
A page devoted to vehicles with only one wheel is here: Motorwheels monowheels They are not all of the unicycle variety.