Bienvenu, my motorbike driver, negotiated the gargantuan potholes and filthy water tankers to reach what was then the front line. The Congolese army had been fighting a rebellion in the east of the country. Most motorbikes carried soldiers, riding with their AK-47s pointed skywards, silhouetted in clouds of dust. The Congolese army is reputedly one of the most corrupt and ill-trained state organisations in the world. One of the soldiers’ biggest grievances is not getting paid. Armed escorts distribute boxes of cash, but not all that money reaches the tatty pockets of their fatigues. Corrupt leaders siphon it off, leaving the troops in penury and inclined towards stealing sprees.

Heading for the front line, I’d been told about a potentially revolutionary change: government employees in Congo, soldiers included, were being paid by the mobile money transfer service M-Pesa. A text message arrives on your phone. You take the phone to an ATM or agent and, with your secret Pin and ID, withdraw cash. Inspired! Corrupt civil servants will be a thing of the past. I had even heard it was helping Congo quash the rebellion – the soldiers around Goma, near the Rwandan border, were getting paid, so morale was high, and they were making gains against the rebels. It could be the first “app” to win a war.

In the remotest reaches of sub-Saharan Africa, people are doing things you’d have considered barely possible, using the basic Nokia you threw away. M-Pesa, styled as the first app for mobile phones in the developing world, has transformed business and banking since it launched in Kenya in 2007. It achieved the holy grail of app-making by doing one thing that everyone needs. Within five years of its launch, 70 per cent of Kenya’s adult population had signed up.

“What’s behind the technology boom in Africa?” I asked the young Danish investor Nikolai Barnwell as he welcomed me to his Nairobi penthouse office. Barnwell’s company 88mph provides “angel” investors for tech start-ups in Nigeria, South Africa and Kenya. He compares the climate for techcoms in Africa now to when Rockefeller invested in oil, or Britain’s textile mills kicked off the Industrial Revolution. “All the stars are aligned,” he said. “It’s never happened anywhere in the world at this speed.”

Data is affordable, sometimes free. Face­book Zero is a simplified, text-only version of the social media platform, designed for developing markets. It can work on 80 per cent of the phones on the planet. The company’s strategy to entice the “second billion” Facebook users is paying off. For some, the name is becoming synonymous with “internet”. I asked a Kenyan smallholder if he had the internet. “No.” Facebook? “Yes.”

Connectivity is good. Mobile internet is brilliant in the cities, and works outside them, too. I’ve sent emails from the clouds above rural South Sudan, one of the least developed nations in the world. And hardware has never been better or cheaper: China’s Huawei broke the $100 (£60) price point for smartphones in 2010.

Anthony Gitobu works in Nairobi for Yum, an 18-month-old food delivery service. Six years ago, he recalled, smartphones were for businessmen and cost £300. Then cheap “knock-offs” came in. They often went kaput, Gitobu said, but, considering the price, “people didn’t care”. Fake phones have since been replaced with improved, equally cheap, Indian and Chinese makes.

Yum experienced a spike in users (and Facebook “likes”) when it enabled its website for mobiles last year. While Gitobu courts social media, he knows it can bite. Kenyans on Twitter use a hashtag, #KOT. They are a tough crowd, flexing their new-found muscle against stereotyping, inaccuracies and duplicity. If you mess up, in Gitobu’s words, “These guys can take you down overnight.”

The benefits of being connected have spurred the tech boom. The most remarkable apps, like M-Pesa, serve everyone from the wealthy politician to the subsistence farmer. Kenyan farmers who used to get ripped off by middlemen can now check the going rate for their crop by texting MFarm on 20255.

Experts agree that most people in Africa will first use the internet on a mobile device. Computers are expensive and require a lot of electricity, but less than a quarter of sub-Saharan Africa is on the grid. A mobile phone lasts for days, and wherever you are, it’s likely you can charge it. Recently I was at a chaotic, weeks-old South Sudanese refugee camp when a young entrepreneur showed me his battery-powered charging point. The plywood bank with three-pin sockets charged 24 phones at a time.

Although hand-held technology in Africa feels limitless, it is not without flaws. At the front line in eastern Congo, I found Joseph, a soldier, sitting on a rock under a tree, wearing baggy fatigues and bling shades. I asked whether he was being paid electronically by phone. He said no, the new system wasn’t working. “But when it does work, will it improve things?” I asked. We were ten kilometres from Goma on the edge of no-man’s-land. Deserted huts separated us from the rebels, their front doors left open, showing that looters had been inside.

Joseph searched my face as if to ask: “Are you mad?” He gestured around him. “What good is my phone? Can you see an ATM? No, I need cash. I’m at war.”

Jessica Hatcher is a journalist based in Nairobi, Kenya