Some thoughts... Golf carts...
A few years back, in the town of Claremore, Oklahoma, (NE of Tulsa about 40 miles, a town with 20,000 people and NOTHING TO DO.) there was a disabled man who worked in town, and would drive his golf cart across town (I think it was a little over a mile trip) to get to work. Well, Claremore police being the <<Expletive Deleted>> that they are, harassed him, told him he could not drive the golf cart, etc. He made a court case out of it, he couldn't drive a car but had to get to work, along those lines. And now, in the state of Oklahoma, it is legal to drive a golf cart on surface streets.
Also, in this state, it is legal to drive an electric motorized wheelchair down the sidewalk even if you are not handicapped.
I've had thoughts in the direction of a motorized unicycle. There are examples to be found on the internet, where people have built unicycles with controllers and pendulum/gyroscopic accelerometers that will stay balanced (front to back) to the tune of $1,500 for the parts. I can't help but ask myself: Why do you need all that? Batteries, a variable speed reversible motor controller, and a 1 horsepower electric motor on a friction drive. Attach the throttle to a long wire to hold it in your hand, build your hand controller so that when you can run the motor any speed in either direction, with the movement of your thumb, and you can reverse it easily. You don't need a special accelerometer and controller. The controller is in your head, and everybody has a 3 axis accelerometer in each ear! It would take practice, but if you can pedal one, you can motorize it. You wouldn't want one that could exceed about 10 MPH, because you want to be able to land on your feet when you fall off. (You almost always land on your feet when you fall off a uni.)
-Mark