Nick D'Aloisio was just 15 when he developed Trimmit in 2011, an iPhone app that condenses web pages into 1,000 characters, 500 characters, or 140-character summaries. That same year he became the youngest tech entrepreneur to receive venture capital funding, gaining $300,000 (£200,000) of investment from Asia's richest man, Li Ka-Shing.
Artist Yoko Ono, actor Ashton Kutcher, Stephen Fry and Rupert Murdoch's wife, Wendi Deng, have since invested in the app, which was rebranded as Summly late in 2011.
Last Monday, D'Aloisio sold Summly to Yahoo for a figure said to be well over £20m. It's a trajectory of success unseen for any British technology entrepreneur, let alone someone who should be studying for his A-levels.
"It's great in one sense as it'll get a whole stack of teenagers writing code, but it's a little bit misleading," says Alistair Crane, the chief executive at the app development agency Grapple. "If he didn't have the backers that he had, he wouldn't have sold for the amount he did."
While D'Aloisio may have got lucky, there's no denying that there's money to be made from apps. "Everything is moving on to the super-computer in your pocket," says Oleg Fomenko, the founder of the radio app Bloom .fm. "People are spending a lot of money on mobile."
Fomenko is just one of the developers hoping to cash in. Across Britain a host of tech entrepreneurs are building apps to get people spending money through their phones as they dream of a million-pound exit like D'Aloisio.
The brainchild of three London cabbies and the entrepreneur Jay Bregman, Hailo has revolutionised the black cab industry. The app allows customers to see Hailo-enabled black cabs around them, order fares, pay by card and keep a record of journeys. The company takes a cut of all fares booked through the app.
It has been trading for little over a year but already has around 10,000 drivers signed up within London, and it has expanded into Dublin, Toronto, Chicago and Boston, with New York, Tokyo, Madrid and Barcelona all in the pipeline.
What makes the app so successful, says chief executive Bregman, is its role as a "Bloomberg box for taxi drivers. It's got one or two features that a driver will look at and say 'Wow, there's definitely a cab driver behind that'."
The driver app offers real-time traffic data, taxi rank and passenger numbers, and allows drivers to track orders, set targets and measure efficiency.
Blippar "turns the camera on your phone into an extension of your eye," according to co-founder Omar Tayeb. The app uses "augmented reality" to add animations and links to real-world images captured on the phone's camera using the app.
At little more than 18 months old, the company has already worked on advertising and marketing campaigns with Unilever, Nestlé, Heinz, Diageo, Xbox, Samsung and Cadbury, and has opened an office in New York.
Its success saw Tayeb, 26, last year named one of London's top young entrepreneurs in the Spirit of London awards, with Summly's Nick D'Aloisio (see opposite).
Tayeb says the next step is to develop technology that can recognise anything, not just from the images Blippar stores on its mainframe. "The way we see mobile going is it will become an extension of you," he Tayeb says. "Not just storing data but giving you better senses."
Paddle aims to make online payments as easy as paying for something in real life – click "Pay with Paddle" at a web checkout and a code is generated that can be scanned with the app on your smartphone. The app stores credit card and address details, so once you've scanned you just click the card and address and you're done.
"The last innovation in online payment was PayPal 15 years ago," says founder Ed Lea. "We're updating for smartphones."
This four-man operation has only been running since May 2012, but is already processing card payments, and, next month, Marks & Spencer is starting a trial of the service.
King.com chief Riccardo Zacconi is an old hand in tech, having survived the dot.com boom of the Nineties, but his company has been hailed as the "poster child for the European gaming industry" by Facebook's European gaming chief.
King's wildly successful Candy Crush Saga and Bubble Witch Saga have dominated both mobile and Facebook app charts and its games are played five billion times monthly. King makes money from in-game purchases of extra lives and advantages, and the company has also recently signed advertising deals with Pepsi and Unilever.
What makes King unique is that its games are synchronised across all platforms, allowing users to stop playing on one platform and pick up where they left off with the game on another.
The company is rumoured to be considering a stock market flotation next year, but Zacconi says he's currently "focused 100 per cent on building the business", planning to crack Asia this year.
Launched in January, Scoopt is designed to let people share their favourite places with friends. "Somebody that you've never met saying this is a really great restaurant doesn't really mean much," says creator Glynn Jones. His app allows you to browse your friends' recommended bars, restaurants, shops, hotels and more, with pictures pulled from Instagram of each venue.
Jones had the idea while in the South of France two years ago when he was wishing he knew of a good local restaurant to go to. While it has only been operational for little more than three months, Microsoft has agreed to promote Scoopt on its Windows 8 phone, and Jones has ambitious plans to monetise the app. In June, he will introduce a shopping feature that allows users to buy from independent shops that are recommended by friends.
Citymapper is a complete journey planner in your pocket, offering bus, Tube, train and cycle information for Londoners.
"I thought there was an opportunity to nail the transport app and London was the city to do it," says the apps creator Azmat Yusef.
Yusef had previously worked on the successful Busmapper app, but felt a fuller app was needed. He and his team built their code from scratch, calculating all journey times themselves. Yusef plans to expand the app to other cities once they've perfected their code.
YPlan allows users to book tickets for events on the night or a night in advance – everything from flamenco dancing to a tour of a gin distillery.
"Being able to offer something a bit quirky has really helped attract customers," says co-founder Viktoras Jucikas, a former Goldman Sachs executive.
Jucikas and co-founder Rytis Vitkauskas recruited employees from Time Out magazine, Ticketweb and Airbnb, the travellers' bed-for-a-night website, to design and curate the app.
As well as last-minute tickets, users are offered such incentives as discounts, free drinks on arrival and waived booking fees. It appeals to promoters and organisers because it gives them the chance to offload unsold tickets, and YPlan makes its money by taking a cut of all tickets sold through the app. The app currently only covers London, but the founders are looking at expanding it.
Aiming to recreate the success in the US of the personalised radio service Pandora, Bloom.fm lets users listen to radio stations based on a selected genre. Users who subscribe can "borrow" their favourite tracks offline to listen to them whenever they want.
"Our proposition is basically like rental space," says Oleg Fomenko, the app's founder. He's hoping to cash in on small-time music consumers, with subscription rates starting at just £1 a month for storage of up to 20 tracks.
Fomenko has worked out deals with most of the major record labels and the app already has a catalogue of 16 million tracks. Fomenko and his team are also working on a web app: "You can listen to our service on the way to the office and when you get to the office you can pick up where you left off."