A method of monitoring an analyte level of a human with a sensor control device comprising an in vivo analyte sensor, and a mobile communication device, the method comprising: downloading and installing, by a user, a first application onto the mobile communication device; downloading and installing, by the user, a different second application onto the mobile communication device, wherein the first application is a sensor interface application and the second application is a user interface application; receiving data, at the mobile communication device, from the sensor control device, wherein the received data comprises data indicative of an analyte level of the human, or raw data received from the in vivo analyte sensor and the method further comprises processing the raw data with the sensor interface application to generate data indicative of an analyte level of the human; determining, by the sensor interface application, whether the user interface application is authorized to access the data indicative of the analyte level of a human, by reference to a compilation of approved applications; if authorized, granting by the sensor interface application to the user interface application, access to the data indicative of the analyte level of the human; communicating the data indicative of the analyte level of the human from the sensor interface application to the user interface application; and causing, by the user interface application, display of the analyte level of the human on a display of the mobile communication device; wherein, if an indication is received at the sensor interface application, that access of the user interface application to the data indicative of the analyte level of the human is to be removed, then removing access of the user interface application to the data indicative of the analyte level of the human. downloading and installing, by a user, a first application onto the mobile communication device; downloading and installing, by the user, a different second application onto the mobile communication device, wherein the first application is a sensor interface application and the second application is a user interface application; receiving data, at the mobile communication device, from the sensor control device, wherein the received data comprises data indicative of an analyte level of the human, or raw data received from the in vivo analyte sensor and the method further comprises processing the raw data with the sensor interface application to generate data indicative of an analyte level of the human; determining, by the sensor interface application, whether the user interface application is authorized to access the data indicative of the analyte level of a human, by reference to a compilation of approved applications; if authorized, granting by the sensor interface application to the user interface application, access to the data indicative of the analyte level of the human; communicating the data indicative of the analyte level of the human from the sensor interface application to the user interface application; and causing, by the user interface application, display of the analyte level of the human on a display of the mobile communication device; wherein, if an indication is received at the sensor interface application, that access of the user interface application to the data indicative of the analyte level of the human is to be removed, then removing access of the user interface application to the data indicative of the analyte level of the human.