Technology that tracks millions of 911 calls from cell phones in the United States every month is being deployed in Middle Eastern and Asian-Pacific countries to track terror suspects — but legal obstacles prevent widespread usage in the U.S., and some critics say this hampers authorities from tracking suspected terrorists and other dangerous criminals on American soil.

Location intelligence, or LOCINT, lets investigators locate a cell phone within 50 meters — meaning if a suspect is carrying a cell phone and authorities know his number, they can follow his "digital footprint" wherever he goes.

Had the technology been in use during the terror attacks in Mumbai in November, authorities could have used it to identify every cell phone operating in the vicinity of the attacks, potentially cutting off the terrorists' main line of communication.

LOCINT's inventor, a Pennsylvania-based company named TruePosition, says the system could also prove vital in investigating a terror bombing in which a device is triggered by a call or text message originating from a mobile phone.

It could also create a "geo-fence" to protect America's borders.

"When you establish a geo-fence, anytime a mobile device enters the territory, our system will be alerted and provide a message to the customer," said Dominic Li, TruePosition's vice president of marketing. "We realize that this has a lot of value to law enforcement agencies outside of search and rescue missions. It gives rise to a whole host of new solutions for national security."

Li said the innovation is rooted in a sophisticated technology called Uplink Time Difference of Arrival (U-TDOA), which uses cell towers to "triangulate" a phone's location in any environment — even if the cellular phone does not have a Global Positioning System that can offer location accuracy to within roughly 30 meters.

"GPS doesn't work well in urban areas and it works very poorly in indoor environments," Li told FOXNews.com. "When life is at stake and every minute counts, GPS is just not the right technology."

Using more than 75,000 location measurement units nationwide, TruePosition also uses its U-TDOA technology to locate an average of more than 5 million 911 calls in the United States per month, or more than 165,000 per day on AT&T and T-Mobile networks.

Company officials say no other mobile intelligence gathering database system can provide such a "unique solution" to enable private enterprises and government agencies to protect citizens and combat crime.

But the U.S. Constitution prevents LOCINT from being used unchecked in the United States. In many cases, law enforcers must obtain a judge's warrant before pinpointing the location of a cell phone or tracking its owner.

"Where federal agents and prosecutors seek to obtain such information on a prospective basis, the Justice Department's Criminal Division recommends that they obtain a warrant based on probable cause," Ian McCaleb, a spokesman for the Department of Justice, told FOXNews.com in an e-mail.

Officials at the DOJ declined to comment on the technology specifically.

"In today's world of rapidly expanding technology, law enforcement must be afforded the tools to perform their duties in real time, particularly in those instances where there is an imminent risk to human life," McCaleb said.

"Without discussing specific services or companies involved, law enforcement can seek court authorization to acquire certain aspects of cell phone location information."

In 2005, a New York judge ruled that the government could obtain a phone's tracking data without a warrant since the user voluntarily chose to carry the phone and implicitly allowed the transmission of tracking information. Critics of the ruling said it violated the Fourth Amendment, which protects citizens against unreasonable searches and seizures.

The Kansas House of Representatives passed a bill last month requiring cell phone companies to cooperate with law enforcement officials during an emergency. The bill, which passed by a 118-1 vote, was inspired by the 2007 kidnapping and murder of 18-year-old Kelsey Smith, whose parents noted a delay in getting their daughter's cell phone provider to cooperate with authorities, the Associated Press reported.

The bill now awaits a vote in the state Senate. If passed, Kansas would be the first state to pass such a law, KCStar.com reports.

"It could've all been avoided if the information had been released as requested," the girl's father, Greg Smith, told the Web site. "Our hope is that other families don't have to go through the hell we went through."

But Overland Park Police Chief John Douglass told FOXNews.com he would not support an "open-ended, non-restricted" system like LOCINT without the issuance of a court warrant.

"Anything can go too far in one direction," Douglass said. "We want to be able to track down a cell phone in an emergency, but there has to be safeguards. We cannot intrude into personal privacy."

Douglass continued, "Are we going to sacrifice everybody's privacy for the occasion when it would be helpful? There needs to be a method to get it on a restricted basis when there's bona fide need."

Meanwhile, LOCINT continues to operate in Middle Eastern and Asia-Pacific nations where no legal restrictions exist for tracking cell phone signals. Citing security concerns, company officials declined to specify which countries currently use the technology.

"[They're] countries extremely concerned with security," Li said.

U.S. military officials in Iraq and Afghanistan did not reply to requests for comment on the use of cell phone tracking there, but a source close to the matter told FOXNews.com that the practice is widely used.

"In Iraq and Afghanistan, I see [cell phone tracking technology] used all the time," according to the source who requested anonymity due to not being authorized to speak on the matter. "I see it being used as often as a helicopter. But [military officials] don't talk about electronic warfare, even if it's widely used."