Your phone can be used to track you whether you want it to or not. Quite deliberately, the only way you can reliably turn off that ability is to turn off your phone and remove the battery. Here is a link and an excerpt of an article explaining it:
http://www.ehow.com/about_5291861_pros-tracking-devices-cellular-phones.html
Since the mid 2000s, the vast majority of cell phones manufactured and sold in the United States have included tracking capabilities. This is the result of legislation passed after the terrorist attacks in New York City, Washing ton, D.C. and Shanksville, Pennsylvania on September 11, 2001. The Federal Communications Commission (FCC) mandated that all cell phones must have this capability in order to make it possible to trace emergency calls. However, the result of this legislation has had consequences far beyond its intended purpose, with both good and bad effects.
How Personal Tracking Works With Cell Phones
1. Tracking someone using a cell phone works in much the same way as a Global Positioning System (GPS) device. The person's location is calculated in relationship to the known locations of a given provider's cell phone towers or GPS satellites. This can be accomplished with a high degree of accuracy, within several feet. This is true whether the phone has specialized GPS technology installed or not. Since most people carry their cell phones with them and leave them on most if not all the time, using a cell phone as a personal tracking device can be very reliable.
I looked up the fine print on mine (windows phone) a bit ago. It uses the technology to detect any wifi connections nearby.