© 2016 IEEE. A new type of sensor network called the demand-addressable sensor network (DASN) is proposed in this paper. The DASN actively acquires the desired information by addressing user demands and delivers the information to appropriate destinations. This is in contrast to the conventional sensor networks that simply send sensed data to users. The DASN is useful for finding the desired information in a short duration of time from a large amount of sensed data generated by a large-scale sensor network. The DASN is constructed with a demand-addressable network that integrates many on-demand reconfigurable wireless sensor networks (ODRWSN) and other existing information and communications technology systems or services, such as Google Maps and Twitter. In addition to the demand-addressing mechanism, the demand-addressable network has an in-network data combining or mashup mechanism. The mashed up data are displayed on the user terminal using an ordinary Web browser without any requirement to install a dedicated application program. The functions of the ODRWSN can be dynamically customized by injecting roles specified by the user. Thus, the user can actively get the desired information by customizing the sensor network function. The main application of the DASN is wide-area disaster site monitoring, for which the DASN features outlined above are suitable. In this paper, the concept underlying the DASN, its architecture and implementation, and experimental results are presented.