Jackie Flear, jailed for thousands of dollars in unpaid traffic tickets, would have spent another month in Northampton County Prison if not for a new ankle bracelet.

The bracelet carries a GPS device that tells authorities exactly where she is and beeps if she steps beyond the perimeters of the invisible cell at her mom's Wind Gap home.

It restricts her movement, she said, but it's better than spending all 76 days of her sentence in a prison cell.

''I'm just very grateful,'' Flear said.

Northampton County is turning to GPS as it expands its house arrest program, an effort that will help ease crowding at its 822-bed prison. The court in June issued an administrative order that allows low-risk prisoners like Flear to serve the last 30 days of their sentences in their homes.

By using GPS, the house arrest program is available to people like Flear who use cell phones but have no home phones, a requirement under the old technology.

Flear was the only one of the 11 inmates the prison was monitoring on house arrest last week that was using the GPS tracker, but prison officials hope to expand it.

''People are tied into technology, and it affects all types of institutions when that technology changes,'' Northampton County Corrections Director Robert Meyers said. ''We don't want that to prevent people from taking advantage of certain programs.''

GPS tracking works through satellites, which recognize a transmitter attached to the ankle bracelet. The location of the person being monitored is sent through wireless technology to authorities.

While the technology is new to the prison, other county agencies -- including the probation department -- have been using it for a decade. It helps track sex offenders and those convicted of domestic violence. Authorities know exactly where they are and would be alerted if they walked into ''hot zones'' -- a victim's home or near schools or day cares.

''Before, when someone was on house arrest, there used to be a window of time when [the offender] was allowed to go to work or treatment and come home,'' said Marie Bartosh, the county's chief of adult probation. ''Now we know when they left, what route they took to work, what time they got there. There's a huge accountability factor there.''

But GPS isn't foolproof. Transmitting the information to authorities is only as good as the wireless service. When an offender goes into certain buildings, such as a warehouse for work, the signal may be lost.

Carbon County officials decided against using it because, they say, its terrain is too mountainous for reliable coverage.

But with cell service getting better over the years, the monitoring is getting better.

''The available coverage and reliability of the communication has gotten better,'' said Steve Chapin, chief executive officer at Pro-Tech, the provider that Northampton uses. And, he said, the device also is getting smaller.

A decade ago, Bartosh recalled, offenders had to carry around a 4-pound box the size of a purse. Now, it's just a few ounces and tethered to the ankle bracelet, making it easily hidden underneath pants.

Still, technology comes at a price. It's $1 a day more expensive than the monitoring equipment that uses a land line. Northampton County Prison charges offenders $7 a day for the land line-based system and $8 for the wireless.

The cost isn't uniform for all counties. The company, the type of device being leased, amount of oversight and other factors can affect the cost to the inmate. Monroe County officials say GPS is too costly to pass on to the inmates.

While Lehigh County has been using GPS tracking for years, authorities require offenders to keep a land line as a safeguard. About 80 of the 90 people on house arrest in Lehigh County also need to take remote breathalyzer tests, which require a land line.

Travis Pezzuto, a Lehigh County adult probation officer in the house arrest program, said land lines are more reliable if an officer has to contact the offender.

''People forget to charge their cell. They run out of minutes on the prepaid cell phones,'' he said. ''Land lines are a more reliable means of communication.''

nicole.mertz@mcall.com

610-778-2253

Robert H. Orenstein contributed to this story.