A security tag affixed to a mobile phone for monitoring, tracking, and securing the mobile phone within a protected region. The security tag includes: a tag antenna operable at a low radio frequency not exceeding one megahertz; a tag transceiver operatively connected to the device antenna, the transceiver operable to receive radio signals at the low radio frequency and generate data signals at the said low radio frequency, in response thereto; and a microcontroller operatively coupled with the transceiver, the microcontroller being configured to cause the transceiver to emit a signal when the mobile phone is exiting the protected region.