Surveillance by variance-based radio tomographic imaging
This video at Youtube is a great demonstration what’s possible but it’s a horrible demonstration what’s possible as well: Surveillance by using wireless networks. Not by tracking an receiver/transmitter, just by analyzing the variances introduced by something that’s moved through electromagnetic fields. You might think that this video is a scam, but just think about your radio where you could improve the quality of a distant station just by sitting a different way in front of it. You will find a more scientific explanation of this method in this paper published by Joey Wilson and Neal Patwari.
And at the end this technologylooks like a SoHo version of a passive radar systems like Lockheed-Martins Silent Sentry ;)