Handle is Boston Dynamics' latest cool robot; they get quicker and slicker as time goes on.
(Handle, the new Boston Dynamics robot)
...this prototype has a battery range of about 15 miles between charges. The efficiency is due in large part to the wheeled nature of the beast. It balances on two wheels, but the design attaches those wheels to two fully articulated legs rather than directly to the frame of the body.
The result is a quadruped that is distinctly not human in appearance but can perform well in similar environments and with similar tasks. Handle is capable of offsetting its body weight, allowing the front limbs to pick up heavy objects while maintaining balance. The combination of both electric and hydraulic actuators let it perform feats like jumping over four-foot high objects. The independence of each wheel is shown off with ramps to simulate uneven terrain.
In his 1954 novel Lucky Star and the Oceans of Venus, Isaac Asimov writes about the hoppers:
Hoppers are probably the most grotesque forms of transportation ever invented. They consist of a curved body, just large enough to hold a man at the controls. There was a four-bladed rotor above and a single metal leg, rubber-tipped, below. It looked like some giant wading bird gone to sleep with one leg folded under its body. Lucky touched the leap knob and the hopper's leg retracted. Its body sank till it was scarcely seven feet from the ground while the leg moved up into the hollow tube that pierced the hopper just behind the control panel. The leg was released at the moment of maximum retraction with a loud click, and the hopper sprang thirty feet into the air...