The presence of IP Multimedia Subsystem (IMS) in operator networks and support for Session Inititation Protocol (SIP) on mobile phones opens up exciting opportunities for developers. This session covers an overview of SIP and how it can already be used to develop innovative SIP applications for Series 60 smartphones. Development processes for both Java and Symbian based SIP applications will be discussed. It will also include demonstrations of SIP development tools and SIP applications developed by Forum Nokia PRO developers. Developers interested in convergence between the mobile networks and the Internet and development of peer to peer applications like multiplayer games, VoIP clients, Instant Messaging, and file sharing clients should attend this session.