At this past weekend's North American International Toy Fair in New York, not every participant was a toymaker. In the back of the huge space was a booth for BuddyTag—a smart wristband that helps parents monitor children within 120 feet. BuddyTag was invented by Willie Wu after he lost his daughter at Six Flags. “His child did everything right—waiting in one place with an employee of the park," said Wu's sister, who was stationed at the booth. The kid was found in an hour, “but it was the worst hour of his life." It also sparked an idea.