A relative of Boston Dynamics' Cheetah robot, which last year managed to outpace the world's fastest man Usain Bolt on a treadmill, is now able to run outdoors untethered. Named the WildCat, the outdoor runner is funded by the Defense Advanced Research Projects Agency (DARPA), and is being developed for military use. With a large (and loud) motor attached, WildCat isn't as fast as its 28mph-plus cousin — it's currently limited to around 16mph on flat terrain. Despite being announced last year, this is the first public demonstration of WildCat, and Boston Dynamics hasn't detailed its plans to further develop the quadruped.
If they ever get close to you, just pull a wire out. I'm sure it'll frick something up in the process.