A mobile terminal is disclosed which includes a near field or RFID tag (41). The mobile terminal (1) communicates with the mobile telecommunications network and is authenticated with that network using the SIM (15). The mobile terminal (1) is operable to obtain security data from the user thereof, such as a PIN or biometric data, or the mobile terminal (1) incorporates a sensor such as a light sensor, pressure sensor, heat sensor, skin resistant sensor or inertial sensor. The input device or sensor is used to confirm the identity of the user or to evaluate whether the user wishes to use the near field tag (41) to make a payment or obtain entry to a building (for example). Data from the sensor is passed to the SIM (15), which issues a command enabling the near field tag (41), via link (43). The near field tag (41) may then be read by a reader. The near field tag (41) may be automatically disabled after being read by the reader, after a predetermined time, or when the stimulus to the sensor is no longer present.