Electric vehicles and hybrids are here to save the environment (or at least kill your fuel bill), but if you listen to some people they're also here to mow down our pedestrians thanks to their ninja-like ways. Nissan's Leaf has already gone the way of sci-fi by offering a Blade Runner-inspired exterior soundtrack to make sidewalk replicants take notice, and now the Prius is joining in on the fun with its own under-hood speaker system. Curiously, this one will be optional, Toyota apparently expecting that purchasers are so philanthropically minded that they'll pay an extra 12,600 yen (about $150) to protect poor pedestrians. You can see how it's supposed to work in the image above, in which a Prius is shown emitting sound waves to deter a toupee-wearing zombie. But, if you'd rather watch a flashy presentation and hear it for yourself, check out the thrilling video after the break. It'll make you wish your auto sounded like a hovercar.