This paper presents novel structural health monitoring techniques for critical members of civil structures using electro-mechanical impedance sensors. The basic concept of this technique is to monitor critical locations of a structure for changes in structural impedance that would indicate imminent damage. In this paper, principal hardware and software issues on this topic are reviewed. An active sensing node incorporating on-board microprocessor and radio frequency telemetry is introduced in a sense of tailoring wireless sensing technology to the impedance method. A data compression algorithm using a principal component analysis is embedded into the on-board chip of the active sensing node. Finally, a method for compensating the temperature effects on the impedance measurements using cross-correlation analysis with effective frequency shifts is presented.