Well, apparently Santa's magic snowball was not enough for the jolly spy, he needed help...So, he created the Elf on the Shelf.
It comes with a very helpful little elf that you put in random places around the house to spy on your kid and each night the Elf flies back to the North Pole to consult with Santa about the child's behavior. In the morning, the elf flies back to the house and hides himself (or herself) in a new place so that your kids never know where he is.
When my wife brought this home, my son, knew exactly what this was and tried to send the elf back to the north pole. Unfortunately, mommy gets what mommy wants, and now when ever my son is a little difficult, mommy mentions that she was going to have a little conversation with the elf to let Santa know what is going on.
Nothing like training future snitches...