The goal of our research is to lay the foundations for a new generation of context-aware multimodal interfaces for car passengers, that support the interaction of the passengers with the car, between the passengers inside the car and mobile internet services, and between the passengers and the road environment. The task-oriented dialog goes beyond the classical in-car command and control interface by enabling information seeking dialogs and by supporting the combination of speech and physical manipulations of tangible interfaces. The external context is taken into account by supporting verbal references to landmarks visible in the surroundings of the car as well as by introducing a novel car2x paradigm. This paradigm foresees on-demand information on the basis of peer to peer (P2P) multi-hop networks between cars and the traffic infrastructure such as traffic signs and road side units. In addition, the multimodal user interface does not focus exclusively on the driver but will target the co-driver and the backseat passengers as well. Hence, the traditional dyadic dialogue systems is extended to multi-party systems that provide role-based access to available devices and services. We will also demonstrate a first implementation of our results in a Mercedes test car.