Every night at 11 p.m. the village of Dörentrup in central Germany is thrown into total darkness. For the past few years, the village's cash-strapped local council has been switching off all the streetlights in the village each evening until 6 a.m. the following morning. In most places, a nightly blackout would provoke outrage as residents find themselves fumbling and stumbling their way home through the dark. But in Dörentrup, they have seen the light, with a new scheme that allows residents to turn on streetlights on demand — anytime, anywhere — using just their cell phones.