Method for tracking at least one mobile device onto a remote displaying unit through a mobile switching center connected to the mobile device by a wireless communication network and through a head-end linked to the mobile switching center and connected to the displaying unit by a second communication network different to the wireless communication network, said mobile device being identified by a mobile device identifier ID M, said displaying unit being identified by a displaying unit identifier ID Disp and being provided with a module for processing messages coming from the head-end identified by a head-end identifier ID HE, said mobile device being provided with a locating unit able to determine its current location and with a communication unit for supporting at least an instant messaging service, said method comprising an initialization phase and an operating phase, a) said initialization phase comprising the steps of: - generating a key K and encrypting it with a password PW shared between the displaying unit and said mobile device, - setting up, in a memory of said mobile device, a first record R1 IDdisp referring to the displaying unit identifier ID Disp and comprising, the head-end identifier ID HE and said key K, b) said operating phase comprising the steps of: - determining the current location of the mobile device by the locating unit of said mobile device and encrypting the current location by using the key K, - transmitting the mobile device identifier ID M and the encrypted current location to the displaying unit by sending a message successively addressed to the mobile switching center, to the head-end and to the displaying unit by means of their respective identifiers, - decrypting the encrypted current location with the key K and displaying said location onto the displaying unit. a) said initialization phase comprising the steps of: - generating a key K and encrypting it with a password PW shared between the displaying unit and said mobile device, - setting up, in a memory of said mobile device, a first record R1 IDdisp referring to the displaying unit identifier ID Disp and comprising, the head-end identifier ID HE and said key K, - generating a key K and encrypting it with a password PW shared between the displaying unit and said mobile device, - setting up, in a memory of said mobile device, a first record R1 IDdisp referring to the displaying unit identifier ID Disp and comprising, the head-end identifier ID HE and said key K, b) said operating phase comprising the steps of: - determining the current location of the mobile device by the locating unit of said mobile device and encrypting the current location by using the key K, - transmitting the mobile device identifier ID M and the encrypted current location to the displaying unit by sending a message successively addressed to the mobile switching center, to the head-end and to the displaying unit by means of their respective identifiers, - decrypting the encrypted current location with the key K and displaying said location onto the displaying unit. - determining the current location of the mobile device by the locating unit of said mobile device and encrypting the current location by using the key K, - transmitting the mobile device identifier ID M and the encrypted current location to the displaying unit by sending a message successively addressed to the mobile switching center, to the head-end and to the displaying unit by means of their respective identifiers, - decrypting the encrypted current location with the key K and displaying said location onto the displaying unit.