Intel's 2010 International Science and Engineering Fair, you could simply let the windshield darken on its own. Two San Diego students (both accustomed to copious amounts of sunshine) rigged a Toyota Prius to do just that by stringing up electrochromic panels, which dim when voltage is applied. The trick is figuring out when and where to apply it, because when the sun is shining the panels themselves all receive the same amount of light. So instead of gauging it at the glass, Aaron Schild and Rafael Cosman found that an ultrasonic range finder could track the driver's position while a VGA webcam measured the light coming through, and darken the sections liable to cause the most eyestrain. We saw a prototype in person, and it most certainly works... albeit slowly. If you're rearing to roll your own, it seems raw materials are reasonably affordable -- Schild told us electrochromic segments cost $0.25 per square inch -- but you may not need to DIY. Having won $4,000 in prize money at the Fair, the teens say they intend to commercialize the technology, and envision it natively embedded in window glass in the not-too-distant future. Here's hoping GM gives them a call. See pics of the Prius below, or check out a video demo of their prototype right after the break.