Has anyone used or recommends a device that your child can wear or put in their backpack in order to keep track of were they are during the day. There is an article on this site about it along with information about cameras that daycare can install in order to check on the kids while at the center. I worry about my kids and just knowing that they're where they're supposed to be would put my mind at rest. Am I over reacting or is this something I should look into? Anyone used it?