One of the biggest drawbacks to today’s smartphones is their lacking battery power – sure, you can do all of your office work while you’re walking in the park, but only for a few short hours. The solution to this problem comes in the form of the Bio-Mechanical Energy Harvester, designed by Simon Fraser University’s Max Donelan. You simply strap a 3.5 lb generator to your knee while you’re walking, and the kinetic movement can create enough power to charge 10 cell phones without bothering your pace. This invention comes in at #33 on Time’s Best Inventions of 2008 list. Click here to check out the other 49 best inventions, and be sure to check out this great interview with the Inventor of this revolutionary device.