This is actually a reality, but I'm posting here anyway since it is very conspiracy minded. After all, just because you're paranoid doesn't mean someone isn't actually out to get you.

http://www.counterpunch.org/amiri07232010.html

According to the Lebanese daily As-Safir, Qazzi confessed to installing computer programs and planting electronic chips in Alfa transmitters. These could then be used by Israeli intelligence to monitor communications, locate and target individuals for assassination, and potentially deploy viruses capable of erasing recorded information in the contact lines. Qazzi’s collaboration with Israel reportedly dates back 14 years.

On July 12, a second arrest at Alfa was made. Tarek al-Raba’a, an engineer and partner of Qazzi, was apprehended on charges of spying for Israel and compromising national security. A few days later, a third Alfa employee was similarly detained.

...

According to the Lebanese daily As-Safir, Qazzi confessed to installing computer programs and planting electronic chips in Alfa transmitters. These could then be used by Israeli intelligence to monitor communications, locate and target individuals for assassination, and potentially deploy viruses capable of erasing recorded information in the contact lines. Qazzi’s collaboration with Israel reportedly dates back 14 years.

On July 12, a second arrest at Alfa was made. Tarek al-Raba’a, an engineer and partner of Qazzi, was apprehended on charges of spying for Israel and compromising national security. A few days later, a third Alfa employee was similarly detained.
If I have your cell phone number, I can actually already track you.

There is a company called Wavemarket which has agreements with most of the cellular companies to be able to submit a phone number and get back a GPS location.

If this is available commercially as a service, can there be any doubt that national security entities have the same or better level of access?

GPS isn't actually necessary - the modern cellular antennas work by keeping a literal track of your location, then focusing a signal directly to you. See Arraycomm.