Spherical soft robots that move by changing their shape with shape-memory alloy wire are under development at Ritsumeikan University in Japan. I was really interested in seeing these robots, having written about the earlier circular soft robots developed by the same team (see Soft Robot Powered By Shape Memory Alloy Spokes).
In the comments to that article, reader coucou astutely asked "couldn't it be extended to a sphere? A ball rolling in any direction ...". And that's exactly what they did - take a look at the spherical soft robot video below.
(Spherical Soft Robots video)
Researchers Yuuta Sugiyama and Shinichi Hirai of the Department of Robotics at Ritsumeikan University, writing in their paper, describe how a soft spherical robot can also crawl and jump.
"...we employ soft actuators to controllably deform a robot body, enabling it to crawl and jump on rough terrain. Self-deformation of the robot body generates the spatial gradient of the gravitational potential energy of the robot crawling on the ground. By charging the elastic potential energy in the robot's deformable body and releasing it rapidly, the robot generates enough impulse to make it jump. Crawling and jumping by deformation enables the robot to be used over terrain too rough for rigid body robots. Additionally, soft-body deformation reduces the risk of injury should the body collide with humans."
Science fiction fans may be thinking that this technology could serve as the basis for the Rovers, the surveillance guardians from the Sixties television series The Prisoner.
Update: 21-Oct-2016: The first time I read about the idea of a shape memory alloy was in Samuel R. Delany's 1966 novel Babel-17; see the entry for tensile memory polarized matter. End update.