Remember BigDog or AlphaDog from Boston Dynamics? It seems that it is now called LS3 (Legged Squad Support System) and it has a few new tricks. It now has a feature that allows it to follow someone.
I think they need to improve it to make it less noisy. Nevertheless, it will definitely be a great help to the Marines (BTW, this program is funded by DARPA and the US Marine Corps) if this LS3 becomes a reality. Check out the video.