There is growing demand for safety-conscious parents to GPS track their children.

Hundreds of Kiwi parents are placing GPS tracking devices on their children for "peace of mind" while they are apart.

Businesses selling the devices, many designed to look child-friendly, say demand is growing – particularly from parents of children prone to running off, like those with autism spectrum disorder.

Most devices, which were accurate to a few metres, sent regular updates to parents' cellphones and alerts when their child went outside a set area.

A principal warns, however, there are better ways to keep children safe.

Sharon Bradley started her Wandering Kiwi business after looking for a product when she had a toddler who liked to run off while she was shopping.

She sold teddy bear and "giggle bug" themed radiowave devices starting at $50, since GPS devices were harder to sync with New Zealand cellphones.

Devices for pets became quite popular among Christchurch pet owners wanting to track their pets during quakes.

There was "certainly a growing demand" for GPS child-tracking, she said.

A Christchurch couple said they bought a GPS device for "peace of mind" when their five-year-old daughter started school this year.

The parents, who declined to be named, said their daughter did not have any behavioural problems or disabilities that prompted the use of the device, which fitted on her wrist.

"We just want to be able to see where she is going and what she is up to. We don't see it as being over protective," the mother said.

"It might not be for all parents, but we don't see any harm in it."

Their daughter was unaware of the device, which sent updates to their cellphones.

They were not sure whether a GPS tracker would be appropriate when their daughter became a teenager.

"We'll probably keep the device for a few years. There are parents who track their teen's phone with the finder apps now," she said.

Auckland entrepreneur and father-of-three Lance Morris started selling a range of GPS trackers about four years ago, when he saw a need.

"There are risks of losing a child, whether it be because someone has taken them or they have fallen down a drain, or you just want to know where the heck they are and know that they're safe."

"It's not a spying thing, it's just a safety thing."

"There's freaks out there."

The small box device, which he sold for $128, could be worn as a bracelet, necklace, or anklet, he said.

The devices could send a text message every minute giving the child's location, accurate to within three metres, and what direction and speed they were travelling in if a parent was concerned about their whereabouts.

"If they are moving fast, you know you have a problem."

There was also a "ring fencing" ability where if a child wandered out of a set perimeter, the parent would receive a text message.

"I'm a parent and I've lost my children a number of times. The moment you lose them just tears your guts out."

Having the GPS information could be vital for police to know in an emergency.

Morris said he used to use one for his 16-year-old daughter, with an agreement he would not track her. "But there was an emergency button so she could press it at any time and I could go and get her. They're absolutely amazing."

Morris did not sell enough to warrant continuing the business, but there were many available online, he said.

GPS World sales manager Angela Williams said the company sold hundreds of devices to families, mainly those with children with disabilities where they were prone to wandering.

Concerns about the devices included privacy and unnecessary radiation exposure.

"For the average child, I would hope people would look at it twice."

Principals' Federation president Denise Torrey said society was anxious and "worried well".

A child wanting to run away would dump them, and so would an abductor, so it was really only useful for genuinely lost children, or those with disabilities, she said.

"A tracking device wouldn't prevent something happening.

"I think it's sad that our society has come to that actually."

It was better to use preventative measures, like having children walk to and from school with people they knew, advising them of basic safety, and telling them to keep in contact with their parents, she said.