A 12-year-old boy has tracked down the thief who stole his mum's mobile phone, using sat-nav technology.
Kristen knew his mum often lost things, so to keep her mobile safe, he helped her download an app onto the phone. It uses GPS - the technology used in sat-navs - to show the phone's location.
When the mobile was stolen, Kristen knew what to do - he was able to track it down online and informed the police.
The police managed to catch the thief and his mum got her phone back too.
Kristen's mum told Newsround she was amazed: "I didn't believe he could track down my phone using this type of technology."
"I thought there's no way a 12-year-old boy could find my phone!"
Suffolk police were also impressed: "The technology was a very effective way of leading officers to the house where the phone was."