Japanese researchers have created prototypes for “soft” robots that can jump, crawl, and roll (even uphill). A detailed summary of their work can be seen in this pdf file. The prototype uses Shape Memory Alloys, or SMAs, by Toki Corporation. By applying a pulse-width modulated signal the alloy is heated and deforms to a predefined shape. Multiple SMAs allow the overall circular form of the robot to be deformed allowing rolling and jumping shapes to be created. A more 3-dimensional version, where multiple circles are used to create a spheroid shape, can also crawl.
Most mobile robots use wheels or legs to create ground locomotion, so this concept is a unique departure from those ideas. Like a lot of research ideas the actual practical applications are limited. Currently SMA are not very energy efficient and have quite a bit of hysteresis in their pre-formed shape. This means your power supply (batteries) and controller may not be able to reside on the mobile shape and that the shapes you form may have a lot of variability.
But imagine thousands of miniature strips of SMAs each receiving tiny currents from a central controller and you’ve pretty much modeled a human joint. You can also imagine how useful robots based on this technology could be in places where energy is readily available and gravity is not a force to be reckoned with. Satellite technology and space exploration might benefit from the ideas proposed by these researchers.