Thousands of American parents, fearful that their children will be abused by paedophiles while trick-or-treating on Halloween, have downloaded software to identify the homes of sex offenders in their neighbourhoods.
The Offender Locator application uses a GPS system built into Apple iPhones to pinpoint the user's location, and then provides a map of sex offenders in the area. It also brings up a photograph of the offender, as well as their address, date of birth and convictions.
The software has been downloaded more than a million times since becoming available in June, the Times reports.
The software, which has been criticised by privacy groups as a tool for vigilantes, has been in the top ten lists of iPhone applications since its launch, and the company behind it is expecting another rise in sales before Halloween at the end of October.
All 50 states in the US require those convicted of sexual offences to sign a register so their location can be monitored. There are up to 700,000 sex offenders on these lists.
Leslie Gharghetta, a mother of two from Woodridge, New Jersey, uses the software to monitor her neighbourhood. "I try and keep an eye on my kids. With Hallowe'en, I am able to see if anybody on the list is located near me," she told the paper.
"There is one offender listed two streets away from me," said Mrs Gharghetta, 31, whose husband is a police officer.
"This tool helps you understand what is going on in your neighbourhood, who's coming or going. People should be alert and know what is going on."
Click to view image: 'Offender Locator'