Wristags transmit a signal to the Base Unit from up to 350 feet when outdoors and up to 200 feet indoors. Because it uses a point-to-point wireless communication system, the ionKids Wristag does not rely on cell towers or satellites to locate your child-so cloud cover or a building's roof will not prevent you from finding your loved ones.
Additionally, every few seconds, ionTechnology™ simultaneously changes the transmission frequency, Wristag ID and corresponding information in the Base Unit, significantly reducing the chances that a third party can scan or monitor a child's Wristag. In addition, each communication between an individual Wristag and its Base Unit will be transmitted on a different frequency, making it possible for multiple Wristags to be used in the same close environment without transmission interference. -Ion-Kids
ION Kids System Finds Your Little One Before You Lose Your Mind
If you don't want to embed an RFID tag in your kids neck, you could also get the ionKids tracking system: