With the concept and application of the Underground Wireless Signal Networks (UWSNs), the global subsurface monitoring in real-time can be achieved. The wireless signal networks use the signal strength variation of wireless sensor nodes in the host medium (i.e., soil in this case) as the main indicator of an underground event or a physical change in soil properties. However, the deployment of underground signal/sensor networks has more constraint than aboveground deployment, because installation and management of sensors are more difficult and the radio signal attenuation is much higher than above ground communication. This paper summarizes practical potential applications of underground wireless signal networks and challenges and possible solutions on underground signal network deployment. The two representative applications of underground wireless signal networks are experimentally evaluated by laboratory simulations.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.