SINCE the invention of the mobile phone, toddlers have been roaming crowded carnivals with phone numbers scrawled up their arms in permanent marker.
But today's parents can keep tabs on their children using GPS tracking devices, panic alarms, temporary tattoos and barcodes.
Alexandra Wenderoth traded Textas for tattoos this week to avoid losing her three-year-old son, Will, and one-year-old daughter, Honor, at the Sydney Family Show.
The 36-year-old from Randwick transferred temporary tattoos, which had been customised to include her contact details, onto her children's forearms. She bought the child-safety tattoos from Kids Kontact, one of dozens of Australian websites offering the product.
''It's just so convenient because [kids] can just charge off and that's it,'' Ms Wenderoth said. ''I was writing on their arms with permanent marker and I just thought there's got to be something better than this.''
The owner of Kids Kontact, Tracey Birch, who sells 30 tattoos for $30, said they were a low-cost way of keeping in touch with your children in case they go missing.
Her online company, based in Western Australia, also offers other child-identification products, including tracking devices, locators that beep when a child moves beyond a designated area, and panic alarms that parents can attach to their child and sound when they are lost.
''It's a distinctive high-pitched beep,'' Ms Birch said of the panic alarm. ''Some parents even use it when their kids are playing in the backyard to let them know when to come in.''
The products are also used to identify children with allergies or medical issues.
One alarm system was referred to Ms Birch by a woman who lost her autistic child in the bush.
''If a child is non-verbal and someone approaches them, they can't communicate to tell them what their mum's name or phone number is,'' Ms Birch said. ''These products can speak for children who can't talk.''
An American website, SafetyTat, even sells quick-response tattoos that act like a barcode and can be scanned using a smartphone to reveal a child's details.