A computer-implemented method for controlling a web-based application, the method comprising: providing, from a server system to a data processing device primary client, a web page that includes a web-based application suitable for execution on the primary client and a uniform resource identifier specifying a control interface and identifying where the control interface is available, the control interface being configured for controlling the execution of the web- based application by the primary client, the control interface being configured to permit a user to control one or more functions of the web-based application from a control device; and transmitting, from the server system in response to receiving a selection of the uniform resource identifier from the primary client, the control interface specified by the uniform resource identifier to the primary client for use by the control device to control the one or more functions of the web-based application; wherein the data processing device primary client and the control device are in data communication over a wireless data communication path; wherein the primary client is programmed to transmit instructions for implementing the control interface to the control device over the wireless communication path and to receive one or more commands from the control device over the wireless communication path; wherein the data processing device primary client and the control device are associated with a same user; and wherein the server system is configured to store a record of associations of the data processing device primary client and the control device with the same user, in response to receiving information identifying an association of the data processing device primary client with the user from the data processing device primary client and receiving further information identifying an association of the control device with the user from the control device. providing, from a server system to a data processing device primary client, a web page that includes a web-based application suitable for execution on the primary client and a uniform resource identifier specifying a control interface and identifying where the control interface is available, the control interface being configured for controlling the execution of the web- based application by the primary client, the control interface being configured to permit a user to control one or more functions of the web-based application from a control device; and transmitting, from the server system in response to receiving a selection of the uniform resource identifier from the primary client, the control interface specified by the uniform resource identifier to the primary client for use by the control device to control the one or more functions of the web-based application; wherein the data processing device primary client and the control device are in data communication over a wireless data communication path; wherein the primary client is programmed to transmit instructions for implementing the control interface to the control device over the wireless communication path and to receive one or more commands from the control device over the wireless communication path; wherein the data processing device primary client and the control device are associated with a same user; and wherein the server system is configured to store a record of associations of the data processing device primary client and the control device with the same user, in response to receiving information identifying an association of the data processing device primary client with the user from the data processing device primary client and receiving further information identifying an association of the control device with the user from the control device.