There are several non-interoperable peer-to-peer (P2P) protocols available today with different functionalities. In order to exploit this functional diversity on mobile devices, we have developed a plug-and-play application platform (PnPAP). PnPAP provides autonomous, dynamic selection between multiple P2P protocols while ensuring the best available network connectivity. In this paper, we introduce methods for utilizing session initiation protocol (SIP) in inter-PnPAP communications. This communication may include downloads of distributed P2P resources such as polymorphic protocol libraries or dynamic state-machine control modules. These components are then used to optimize connectivity management between heterogeneous wireless access networks. In addition, context information may be exchanged between mobile nodes in order to facilitate extended service availability, operability and quality. We analyze the feasibility of merged P2P and All-IP (including SIP) architecture through the novel use of a specialized SIP server and the leveraging of the emerging instant messaging capabilities of SIP. Preliminary measurement results from the prototype implementation on a Symbian platform and test-bed, with overhead and latency analysis, illustrate the feasibility of this approach.