Recently users have come to demand a natural user interface (NUI) so that they can operate devices naturally, as an alternative to a graphical user interface (GUI). At Fujitsu Laboratories, with the aim of achieving an NUI, we are developing touchless user interfaces that make it possible to monitor users’ behavior through intelligent sensing technologies, such as gesture recognition, eye tracking and speech recognition, and then understand users’ intent to enable them to operate a device in a natural way. It is difficult to achieve this by using individual sensing technologies. Therefore, we have developed a way to ensure a device operation by integrating multiple sensing technologies for natural motion detection. Both gesture recognition and eye tracking technologies are combined in the developed interface, which gives the users the feeling that they are interacting more naturally and effectively with devices than they would if only individual sensing technologies were utilized. This paper describes an overview of the developed sensing technologies, the merits and problems regarding their combination, the developed interface, and future work.