The Dynamic Device Association (DDA) framework presented in this paper provides service discovery and secure device access for mobile users. We discuss scenarios and requirements for enabling mobile users to find and access co-located (mobile) multimedia services on demand. As example, we use the dynamic discovery of IP telephony services in a network that an application on a mobile device can locate, personalize and control on behalf of a user. We examine existing protocols such as SLP and UPnP and derive a different, more general solution that addresses the issues of scalability for service announcements and security for device access. We outline the DDA approach with its five phases: service discovery, selection, device association, application protocol operation, and device dissociation. We show how the DDA approach can be used to bootstrap arbitrary application protocol sessions and present a concrete protocol specification and its implementation. 1