Sarcos's next-gen leg can swing freely to reduce the energy cost of walking.http://www.popsci.com/scitech/article/2008-04/building-real-iron-man
I can't believe they're still
stumbling on the power source. I've already got that part nailed. My solution isn't cheap (about $10k), and it ain't quiet, but it will provide more than enough power, it's free of rotational inertia effects, and it's made of parts you can buy today.