In society where the numbers of elderly people is growing rapidly, there is an urgent need to have smart ambient environments. It is important to design novel user interfaces for senior citizens to ease their daily lives. This paper presents a projection based display system for elderly people with memory problem. The proposed user interface for the system is also described as well as the required infrastructure of sensor networks and user's process detection. Elderly people wearing the system can interact by tapping physical surfaces surrounding them (such as walls, tables or doors) as an input surface.