A system for monitoring and/or controlling a vehicle comprising: data transfer means for receiving data signals transmitted on a vehicle data bus relating to the status and/or operation of one or more vehicle systems or devices, the data transfer means being operable to convert the data signals into data messages corresponding to the data signals; and a transceiver provided onboard the vehicle for wirelessly transmitting the data messages relating to one or more of said received data signals to a mobile communications device for display to a user, the transceiver being arranged to transmit the information relating to the one or more received data signals from the vehicle to the mobile communications device via a web server, web portal or other internet-connected host system, wherein the web server, web portal or other internet-connected host system is arranged to receive control messages from the mobile communications device and to transmit said control message to the transceiver, and wherein the transceiver is arranged to receive control messages from the web server, web portal or other internet-connected host system, the data transfer means being arranged to convert the received control messages into data signals and transmit the same onto the data bus for controlling one or more vehicle systems, functions or devices, wherein the web server, web portal or other internet-connected host system is arranged to receive a user initiated status request control message from the mobile communications device and to transmit said status request to the transceiver and wherein the transceiver is arranged to receive a status request control message from the web server, web portal or other internet-connected host system, the data transfer means being arranged to convert the received status request control message into data signals and transmit the same onto the data bus for determining the status of one or more vehicle systems, functions or devices; and wherein the data transfer means is configured to: suspend transmission of data messages and reception of control messages by the transceiver after a first predetermined period after the vehicle engine is stopped; and cause transmission of data messages and reception of control messages by the transceiver to continue intermittently for a second predetermined period after the first predetermined period has elapsed, by switching the transceiver to a mode in which the transceiver is activated intermittently. data transfer means for receiving data signals transmitted on a vehicle data bus relating to the status and/or operation of one or more vehicle systems or devices, the data transfer means being operable to convert the data signals into data messages corresponding to the data signals; and a transceiver provided onboard the vehicle for wirelessly transmitting the data messages relating to one or more of said received data signals to a mobile communications device for display to a user, the transceiver being arranged to transmit the information relating to the one or more received data signals from the vehicle to the mobile communications device via a web server, web portal or other internet-connected host system, wherein the web server, web portal or other internet-connected host system is arranged to receive control messages from the mobile communications device and to transmit said control message to the transceiver, and wherein the transceiver is arranged to receive control messages from the web server, web portal or other internet-connected host system, the data transfer means being arranged to convert the received control messages into data signals and transmit the same onto the data bus for controlling one or more vehicle systems, functions or devices, wherein the web server, web portal or other internet-connected host system is arranged to receive a user initiated status request control message from the mobile communications device and to transmit said status request to the transceiver and wherein the transceiver is arranged to receive a status request control message from the web server, web portal or other internet-connected host system, the data transfer means being arranged to convert the received status request control message into data signals and transmit the same onto the data bus for determining the status of one or more vehicle systems, functions or devices; and wherein the data transfer means is configured to: suspend transmission of data messages and reception of control messages by the transceiver after a first predetermined period after the vehicle engine is stopped; and cause transmission of data messages and reception of control messages by the transceiver to continue intermittently for a second predetermined period after the first predetermined period has elapsed, by switching the transceiver to a mode in which the transceiver is activated intermittently. suspend transmission of data messages and reception of control messages by the transceiver after a first predetermined period after the vehicle engine is stopped; and cause transmission of data messages and reception of control messages by the transceiver to continue intermittently for a second predetermined period after the first predetermined period has elapsed, by switching the transceiver to a mode in which the transceiver is activated intermittently.