In this day and age of pervasive technology, anybody's cell phone, on or off, is the culprit. Rather than go through a dry dissertation on how this technology works, we will direct you to a website that will give you a live demonstration which should chill you to the bone.
First, some ground rules. The demonstration works if your cell phone is on, but it is more effective if you turn it off. Secondly, you may be concerned about privacy issues on the website we are directing you to. If that is the case, please read the privacy statement before you proceed. Rest assured, however, this site will not compromise your privacy. The site does not retain any personal information.
Once you are comfortable this site is legitimate and not harmful, enter your cell phone number in the space provided and press the button labeled "Start Searching." One final warning: As you watch this website do it's processing, hold firmly onto your socks, because they are about to be knocked off.
As always, we hope you have a great weekend.