A busybody dad has created an app to stop kids from ignoring their parents' phone calls or texts.
Nick Herbert was unable to contact his son, Ben, so came up with a way of stopping the 13-year-old from screening his calls.
The 45-year-old built the ReplyASAP messaging app which takes over the recipient's phone screen and sounds an alarm - and doesn't stop until it is answered.
Parents are told if their kids have seen their message and if the troublesome teen's phone is turned off then a message pending sign will show on the sender's phone.
Now Mr Herbert, from West Wickham in London, is selling his creation to help stressed out parents across the country keep track of their children.
'My son started at Langley Park School for Boys a couple of years ago and has a smartphone', said Mr Herbert.
'I thought this would make getting hold of him easier, but it doesn't at all.
'In fact, he is always playing games and has the phone on silent. It drives me crazy', he said.
He hopes the app will make their relationship better as a result.
'It will alleviate the stress when I can't get hold of him as I will know that he has seen my message', he said.
However, currently the app only works with Android and his 13-year-old Ben has an iOS phone.
He is keen to get his app working on iPhone devices as soon as possible.
The process of building the app - which is currently only available in the UK - has taken eight months and has been complicated and expensive, but Mr Herbert believes it will take off.
The app costs 99p ($1.28) to snoop on one person, £2.49 ($3.21) to track four people, £6.99 ($9) for ten people and £12.99 ($16.73) for platinum, which connects with 20 numbers.
All users will be able to connect to one child for free when they download the app.
Parents might be pleased but Mr Herbert acknowledged teens might be wary of the intrusive invention.
'As they are teenagers I realise they aren't going to be massively keen. My son hasn't really said anything negative about the app. It is all about him understanding why it's there', he said.
'If I have something important to say I will send an urgent message. Hopefully It will make things a bit easier.
'Will it be the bane of his life? Maybe, I'm not going to be using it all the time to speak to him. It is supposed to be a failsafe.'