Tiny networked sensor devices will be disseminated over our physical life space, and take a significant role in realizing a ubiquitous computing environment. As sensor network technologies and its applications are still at its early stages, the architecture of the sensor network heavily relies on the applications. We believe it quite essential to come up with various kinds of applications, and obtain sufficient knowledge of sensor network architecture and its peripheral technologies through demonstrations. In this paper, we introduce our sensor network applications and present the way sensor network is used in them.