Our research is at the crossroads of two main complementary areas: agents for intelligent systems and human-computer interactions. The prospect of highly natural interfaces, in which interaction between user and computer is mediated by lifelike agents, is currently one of the major steps leading to the acceptance of relevant and practical agents system by people. In this paper we illustrate our approach which takes into account both the evolution of the user interface technology and the emergence of ubiquitous computing in order to propose a proactive adaptive assistance through an agent named X-CAMPUS (eXtensible Conversational Agent for Multichannel Proactive Ubiquitous Services). It aims to assist proactively user in her daily tasks thanks to its ability to perceive the state of the environment and to communicate effectively according to the user's current situation.