The user interaction in mobile phones has been traditionally based on key behaviors that users have adapted around their mobile devices. Although this type of interaction could be suitable for some contents, it could be improved from the point of view of the usability. In this paper we present a new user interface based on 3D navigation oriented to mobile phones. To enhance the user experience, we have developed a new interface based on 3D real-time graphics where users interact by means of natural movements of their devices. The goals of this development consist in enhancing the user interaction and accessibility to web content or interactive multimedia applications by means of avoiding a key-based, or a mouse-based, navigation and proposing a software solution adaptable to multiple and different mobile devices. In this sense, the user inputs can be detected by different input devices such as accelerometers or cameras, as well as the traditional keypads. Since mobile phones with on-board digital cameras are now widely available at low cost, the proposed 3D user interface exploits the acquisition capabilities of these input devices. In this sense, a differential algorithm has been applied in order to estimate phone movements from video images. The results of the performance evaluation of the 3D user interface shows that the proposed algorithm not only obtains a motion and tracking under extreme lighting conditions, but also adds an insignificant overhead to the system performance. Finally, a 3D environment has been designed to evaluate the performance of the presented approach, which has been successfully tested in actual users.