A third of America's population struggles to sleep through the night. For many of us, stress and anxiety play a big role in that. Some designers believe they can help us tackle these problems and calm our minds. The sleep-aid market is a multi-billion dollar industry, so it's no wonder companies are trying to design solutions for us. But can apps and gadgets designed to help us sleep, and keep us calm, really help? Or are they just a kind of digital snake oil?