The invention provides a quality of service monitoring device (12) for use with a user equipment comprising a base platform (14); and an external communication module (24) adapted to receive from an external source one or more listener modules and/or detector modules for incorporation into the base platform (14). The base platform (14) is coupled to the external communication module (24) to receive one or more listener modules (20) and detector modules (22) and is adapted to install received modules to extend the functionality of the base platform (14) so as to perform the functionality of the installed modules. A corresponding method is provided. There is also provided a quality of service monitoring apparatus, for use on the network side, as well as a corresponding method.