A tech start-up aims to rid teachers of the stress of counting heads on school trips with a new app which triggers an alarm if any children wander off.

The Hug Group formally launched its office in Dartford with a demonstration of its software which it hopes will attract the attention of 25,000 schools across England.

Bosses invited pupils from Dartford Bridge Community Primary School to try out its devices ahead of a term-long trial where teachers will test out the kit on trips.

They also showed children from Years 3-5 the 3D printer they use to make prototypes of their lanyards and wrist alarms before final designs are sent to high-end manufacturers.

Co-founder Nick Charge had the idea for the product, named ClassHug, when his wife came back exhausted from a school trip to Southend after keeping an eye on five children with her.

He said: “She was so stressed I thought there has got to be a better way of managing this.

“I thought: ‘Why not use technology which sends out a signal to help her track the kids?’”

“We can’t find anyone who does this. It’s an individual product...” - Nick Charge, Hug Group

He secured the services of Andy Davies, now the company’s chief executive, having previously worked together at fintech start-up CloudMargin, which Mr Davies launched in Silicon Roundabout in London in 2014.

He sold it to venture capitalists and it is now worth more than $10 million.

The pair’s latest enterprise uses an iBeacon, a piece of hardware created by Swatch Group, which transmits a signal several times a second.

This is placed in a wristband or lanyard worn by pupils and tells a teacher’s iPad or mobile phone where they are.

Mr Charge said: “We can’t find anyone who does this. It’s an individual product.”

The duo had run their new business from spare bedrooms in their homes in Surrey and Essex before launching the firm’s first office in Nucleus Business Centre in August.

Mr Davies said: “This is an area where there’s a lot of people and a lot of innovation.

“The transport links are amazing. This is a great place to do business.

“It ticks so many boxes for us as a start-up and we have potential to grow here.”

Dartford MP Gareth Johnson was invited to the offical launch of the Hug Group’s office and described the technology as “mind blowing”.

He said: “It is very innovative. There’s clearly a gap in the market for this kind of product.

“We deal with a lot of school parties who come to the Houses of Parliament who need to ensure their children are safe and this sort of product does exactly that.

“It provides reassurance to teachers and parents know their children are being properly minded.”

"There’s clearly a gap in the market for this kind of product..." - Dartford MP Gareth Johnson

Dartford Bridge school’s assistant head Alison Bates said: “It’s a really good idea. If you go on a trip to London it’s busy as there are so many schools around.

“We divide the children into smaller groups but if you have a parent helping they have to be very observant. They might not be used to having five to six children to keep an eye on.”

The product also impressed pupils.

Eight-year-old Anthonia Kolajo said: “I think it’s a great idea because some children like to walk off. Once I have got lost in a shop.”

Ellis Stone, aged nine, said: “Sometimes you don’t know how far away you are but with this the teachers can figure it out. Also, it’s waterproof so if it gets splashed it won’t get broken.”