Swaddle cloths for your baby perform much the same function when it comes to getting the little blighters to sleep. The baby's arms are held immobile, and struggling tends to help tire them out even more. Certainly Lex will not sleep unless securely swaddled. It's amazing to watch how often he changes from screaming and not wanting to be put down, to comparitively quiet and restful once swaddled.
But like a madman, he screams and struggles against it every single time.