Nanogenerators

"Scientists at the Georgia Institute of Technology are working on a new type of nanogenerator that could draw necessary energy from flowing blood in the human body. The hope is to incorporate the new nanogenerator into biosensors, environmental monitoring devices and even personal electronics that will require no fuel source, internal or external. Once completed, this new cellular engine could find various applications, even beyond medicine."

http://news.softpedia.com/news/Nanogenerator-Could-Draw-Energy-from-Human-Blood-60580.shtml

Sure, that's exactly what we need. Ready made technology for the machines to harvest energy from our blood when they revolt.
Don't come crying to me when they're farming us like cattle to get their fix of jiggawatts.