Here's a whole different way of thinking about wireless network technology as reported by Technology Review...

Wireless Network Modded to See Through Walls

As TR reports, the University of Utah research involves using the 802.15.4 wireless protocol used in the ZigBee Personal Area Network (PAN) specification. A statistical model is used to determine is something is moving behind a wall by analysing the variance of the signal strength in a peer-to-peer network (34 nodes were used in the experiement. You can find the original paper available for download here...

Through-Wall Tracking Using Variance-Based Radio Tomography Networks

You can see a different way of achieving similar results explained in this report of research that was conducted a couple of years ago...

Oceanit Sense Through The Wall Technology on KGMB9 news

It also uses RF (radio frequency). However, this technology uses RF to detect heart rate and respiration. An earlier application of this technique was used to develop a sensor bed to read a patient's vital signs with attaching physical sensors.

Full disclosure: My day job is as a project manager for Oceanit. I was not, however, involved in either of the projects described above.