Sleep trainers for kids are gadgets you buy, then replace. Luna is an app: an old Android or iPhone becomes the clock, and free 3D printed cases turn it into a real bedside object. Everything runs over your home WiFi, parent phone to clock, paired by PIN and encrypted. What stands out: a live listen and talk call to the room, your own music and alarm sounds, weekly sleep schedules and naps, and a glowing nightlight border you set from your phone.