A child safety boundary alarm system, for warning caregivers of a dangerous situation when a child passes a boundary near a hazard such as a swimming pool. The system includes a base unit, an auxiliary unit, and a bracelet worn by the child. The caregivers have portable electronic devices. The base unit and auxiliary unit have annunciators and the system is connected to a computer network. When the base unit determines that the child has crossed the boundary, audible and visual warnings are generated by the annunciators and notifications are provided to the electronic devices of the caregivers using the computer network.