In this article we introduce the concept of generalized notification services (NSs). NSs are a simple class of services for mobile and wireless terminals, but nevertheless there are many useful services which can be modeled as NSs. Mobile and wireless terminals (MWTs) in our sense are handheld computers with a wireless interface for data communication (e.g., GPRS, UMTS, or WiFi); examples of MWTs are cellular phones, personal digital assistants (PDA), and smart phones. Mobile services are functionalities offered by one or more remote computers (server or back-end systems) to a MWT (client). Because of the mobility of the MWT, at least the first part of the route for the necessary data communication with the server is realized using wireless standards like GPRS, UMTS, or WiFi.