A new GPS tracking device can be slipped into a vehicle and it'll track where a person drives, when they stop and how fast they go.

It costs less than $200, and parents of teenagers such as Kansas City, Kan., mother Rebecca Zirkle say they love it.

Local police, however, warn women to watch out for them.

"It's not a spying technique for me as much as it is an ability to get to her if she's in trouble or if she shows up missing," Zirkle said. "I want to be able to save her."

Zirkle's daughter Sara also has two speeding tickets. With the GPS device, every time Sara speeds, her mother fires up the computer and finds out about it.

There's nothing illegal about it if the parent using the device owns the car and wants to track their teenager, but a stalker could hide the device in a vehicle to spy on a victim.

Police said it has already happened.

Jackson County, Mo., prosecutors charged a 20-year-old Kansas City man, Raymundo Munoz, with violation of a protection order after his estranged girlfriend found a GPS tracking device hidden on her gas tank.

Munoz denies stalking his ex and said he didn't put the device on her vehicle.

Court documents tell a different story.

The young woman said she became suspicious after Munoz threatened her, saying, "Watch what you do because I know if you are lying."

Sgt. Kevin Colon works in the Kansas City Police Department's domestic violence unit and said police across the country are starting to see similar cases.

The laws have been slow to catch up with technology, so women should trust their instincts, Colon said.

"If they feel that they're running into the offender far too often, it might be a good idea to find somebody to enlist some sort of counter surveillance equipment to see if there's any signal being emitted from the vehicle," Colon said.

The police department doesn't have a device to detect hidden GPS, he said.

But GPS device are not all bad, he said. They're great at tracking Alzheimer's patients, stolen cars and speeding teenagers.

Still, people have found a way to exploit the technology and Colon said women in abusive relationships should watch out.

Munoz was charged with violation of a protection order, because there's no law on the books yet to address electronic stalking.

Rose Brooks Domestic Violence Shelter is so concerned about hidden tracking devices that they just sent out a safety planning sheet to warn staff and the women they help protect to watch out for what could be hidden in their cars.