Most parents find it annoying when their teenagers don’t pick up their phones.

But when Nick Herbert was unable to contact his son Ben, 13, he decided to do something about it.

Mr Herbert, 45, of St David’s Close, West Wickham, built the ReplyASAP messaging app.

The app sends messages which take over the recipient’s phone screen and sounds an alarm.

Troublesome teens can’t get rid of the message or the alarm until it is interacted with.

Parents are then told if their kids have seen their message. If the teen's phone is turned off then a message pending sign will show on the parent's phone.

Now Mr Herbert is selling his creation to help stressed out parents across the country.

“My son started at Langley Park School for Boys a couple of years ago and has a smart phone. 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!

“I’m hoping the app will make our relationship better. It will alleviate the stress when I can’t get hold of him as I will know that he has seen my message.”

Parents might be pleased but Mr Herbert acknowledged teens might be less sure.

He said: “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.

“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,” he added.

The process of building the app has taken eight months and has been complicated and expensive. Now Mr Herbert must see if his idea will take off.

He hasn’t always been sure that other parents will be as happy with ReplyAsap Messaging App as he is.

Mr Herbert said: “I was speaking to some people and saying what the apps does and why I built it. A person said: ‘why don’t you just phone him because that I would do.’

"I thought ‘maybe it is just my son who has his phone on silent the whole time. Do everybody else's’ kids keep their phones on?’

“But after speaking to other parents I think there is an issue that the app would address. It seems to be something that does resonate.”

Mr Herbert has one problem left to overcome, his app only works with Android and his son has an iOS phone. Understandably Mr Herbert is keen to get his app working on iPhone devices ASAP!

More information, including pricing for the app, can be found at www.replyasap.co.uk.