Georgia Tech's Zhong Lin Wang authored an article that appeared in the April issue of Science and is now available online, titled Piezoelectric Nanogenerators Based on Zinc Oxide Nanowire Arrays (PDF format). It's a complex technology but a simple idea: bending tiny wires back and forth generates usable amounts of electricity. The military wants to put them in soldier's shoes to recharge their equipment as they walk. They have all sorts of potential applications in the field of "perpetual computing"; self-powered devices such as micro robots, underwater nanobots, smart dust and robomotes. For more technical details, see Wang's publications list for lots of papers on nanowires, nanowire arrays, and other tiny subjects.