When a three-year-old New Zealand boy told his mother three nights in a row he'd seen a "man with a light" outside his bedroom window she thought it was just nightmares.

"I thought, obviously he's just had a bad dream," the boy's mother Melissa Rodrigues said.

But on June 26 the parents woke early to hear their son screaming in terror.

"At 5.30 in the morning he let out an absolutely gut-wrenching scream from his room … I knew something wasn't right," Mrs Rodrigues, a children's book author, told Stuff.co.uk .

The boy and his father went outside their home in Wellington's north to find footprints in the frost and their garden gate wide open.

A toolbox and some extension cords had recently disappeared, so they called the police and thought about what to do next.

The boy was sent to stay with his grandparents the following night while mum and dad looked at beefing up their home security.

Security cameras were an expensive option, so the couple downloaded a smartphone app called Salient Eye which uses the phone’s camera to capture images when movement is detected and emails pictures to the user.

They fixed the camera to their garage and left the back light on, believing the camera would not be able to pick up decent images in the dark and the light might ward off any intruders.

The couple then settled into the lounge room for an all-night stakeout.

Around 4.40am a fast flow of emailed pictures came in showing someone moving about the backyard and all the way up to the back porch.

"It gave me the shock of a lifetime because, even though I was waiting for it, I wasn't expecting to see him," she said.

They called the police who arrived in no time with a dog with the whole drama being captured and sent through to their email.

"We were sitting in the house watching it all through the app. It was brilliant," Mrs Rodrigues said.

A 15-year-old boy well-known to police and who had been reported to welfare for stealing cigarette butts, admitting to stealing from several of the Rodrigues' neighbours, Scoop.co.nz reports.

Senior Sergeant Anita Dixon said the incident "was able to be sorted out very quickly, thanks to the excellent information supplied by the family, and the police working quickly, together with the help of the mobile phone app".