The system and method provide for a small, low-power device, e.g., a Bluetooth® device, in a carryable or wearable form, that allows a controlled device to respond to the presence of the user. The device may be worn on one's person and allow other devices, by means of Bluetooth® pairing and protocols, to detect the presence of a user. The controller or controlling device may emit a signal in the vicinity of the user to allow the controlled device to know whether or not the controlling device is present, and the signal may be a pulse of data that is transmitted every few seconds. The pulse of data between the transmitter and the receiver may be encrypted to be used for higher-security applications as a means of dual-factor authentication. The presence of the user may be employed to control a device, e.g., to control access to a computer, to unlock/lock doors, to turn lights on and off, and so on.