The quality attribute concerning usability is generally of significant importance to systems. The area of Human Computer Interaction, HCI, especially handles several usability aspects. This degree project emphasizes HCI in a context of, so called, Smart House. The report is divided into three main sections: theory, application, and measurement results. In the theory section we will present about the context of HCI and the content of HCI, such as HCI model and goals of HCI design. In the application section we discuss the use of mobile phones as a device to remotely control devices of smart houses, and present a system developed to support such services. In order to make the system more attractive, we decided to design it for two categories of operations, menu operation and direct-touch operation mode. Finally, we have used questionnaires for reasons of measuring user satisfaction. Through investigation and analysis of the result of this, we come to the conclusion that system usability is good.