I dont know if this will be fast enough, but a very novel item i seen in a cafe was a teddy bear that rode a bike along a high wire.
It was a very simple design with 1 motor, the bike was not powered and it worked on gravity, one end of the wire was attached to a wall with a swivel joint, the other end was attached to a arm on a motor, as the motor turned slowly the wire would be raised as the arm went to 12:00 oclock and the bear would ride the bike backwards, and as the arm came around to 6:00 oclock the wire would be lower then centre and the bear would ride his bike forward.
It was very simple and enjoyable to watch, most importantly the kids all shut up and watched the bear.........Ahrrrrr... coffee in peace and quite.
Pete.