The Swiss Army knife of gadgets, smartphones make for very good alarm clocks. They’re comforting to sleep with, keeping digital life within arm’s reach, and slide discreetly beneath your pillow, faithfully blaring a sound of your choice every morning, mere inches from your head. This convenience comes at a cost: Plenty of research shows that a smartphone screen’s cool blue light makes it harder to sleep, impairs vision, suppresses melatonin, and throws the body’s circadian rhythm completely out of whack. (The National Sleep Foundation recommends ending the use of electronic devices at least thirty minutes before bed.)