The case is directed to portable or client devices that are adapted to instantiate a client application that is communicably coupled to one or more remote host services. The client application is also adapted to cause a display of a graphical user interface having various regions. A first interface region of the graphical user interface may be associated with a first microfunction installed on the device and a second region may be associated with a second microfunction installed on the device. The various microfunctions may enable the client application to interface with one or more remote host services and may be shared across different client applications. In some cases, multiple microfunctions are used to define a custom, user-defined integrated application.