For years, the well-connected world leader would use nothing but a BlackBerry to get their email on the move – and it is still Barack Obama's phone of choice. He uses a model specially enhanced by the US National Security Agency. But the news earlier this month that the White House Communications Agency is testing other phones, including models by Samsung and LG, sent shivers through fans of the struggling Canadian smartphone company, which has just announced an annual loss of $5.8bn.

For a world leader, security is much more than just having a passcode on your phone; it also means protecting it against attempted incursions from all the amateur and professional hackers, and more importantly spy agencies, who want to know to whom, when, what and where you have been speaking and reading. For a country's leader to have their phone eavesdropped is the ultimate failure of their national spy agency, and a huge loss of face. With enhancements, BlackBerry has been the spy agencies' phone of choice to guard against that so far. Now, though, Apple and Samsung – the two largest makers of smartphones – are starting to knock on the security services' doors.

And what if BlackBerry goes away? Though it may have pulled out of a death spiral, BlackBerry's position as the phone of choice for top executives is less clear – and Apple has been touting (pdf) ever-improving security on its iPhone, which has been edging out BlackBerrys even in financial institutions such as Goldman Sachs, once a redoubt for the keyboard-reliant phones. Yahoo, Pfizer and Halliburton have all said sayonara too.

As rival devices improve their security, it could only be a matter of time before Apple or Samsung becomes the US leader's phone – perhaps not during Obama's presidency, but in his successor's. Though the White House press secretary has insisted that "the executive office of the president is not participating in a pilot programme" to replace Obama's BlackBerry, it might only be a matter of time – though if Hillary Clinton succeeds him, her well-known affinity for it could extend its survival just a little longer.

Germany

Angela Merkel uses a Nokia Slide. Photograph: Fabrizio Bensch/Reuters

Angela Merkel's mobile became the most famous phone in world politics when it emerged in October last year that the NSA had been monitoring the chancellor's calls. But she has at least two phones she uses on a regular basis: the one that was allegedly monitored by US intelligence services, a Nokia 6260 Slide, was reportedly used for party matters only. For state affairs, Merkel uses a BlackBerry Z10, fitted with an encryption chip by Secusmart. The Düsseldorf company insists its software remains hack-proof and continues to market its device as the "Kanzler-Handy", the chancellor mobile. Philip Oltermann in Berlin

US

One of Barack Obama's first battles when he arrived in the White House in 2009 was to keep his beloved BlackBerry, despite objections from administration lawyers and the secret service. "I'm still clinging to my BlackBerry," he said at the time. "They're going to pry it out of my hands." Ever since, the US president has been permitted a modified BlackBerry handset, with enhanced encryption. Only a handful of senior White House officials and family have his personal email address. Three months ago he told a group of young people: "I am not allowed, for security reasons, to have an iPhone." Paul Lewis in Washington

Pakistan

Nawaz Sharif has been spotted using iPhones and Samsungs. Photograph: Petr Josek Sr/Reuters

In a country where unusual phone numbers are traded as prestige items it's not surprising to see well-heeled Pakistanis carrying around at least two high-end smartphones wherever they go. Nawaz Sharif, the three-time prime minister of one of the world's most populous countries, has been spotted using iPhones and Samsungs. But these belong to members of his entourage who act as gatekeepers to their boss. The only phone he carries is a far-from-fashionable BlackBerry Bold. A fan of the ailing phone maker's messenger service, Sharif uses it to stay in touch with his family and close political allies who are privileged to have his number. Jon Boone in Islamabad

Russia

Vladimir Putin looks at a phone. He claims not to use one himself. Photograph: Ria Novosti/Reuters/Corbis

The Russian president, Vladimir Putin, is famous for claiming to not have a mobile, unlike the prime minister, Dmitry Medvedev, who is known for his love of Apple products and became one of the first owners of an iPhone 4 when Steve Jobs gave him the still-unreleased phone in Silicon Valley. In 2006, Putin reportedly said he had many mobile phones but did not use any of them because he did not have time and preferred to use other methods of communication. But in 2010, the president said he did not have a phone at all: "If I had a cellphone, it would ring all the time."

But Putin's aversion could also be tied to security concerns ingrained in him from his time as a KGB spy. The president is also known to avoid the internet, instead preferring to get his information from regular reports by his intelligence agencies. A television documentary from Putin's office in 2012 showed red folders on his desk – probably intelligence reports – and a bank of old-fashioned beige telephones. Alec Luhn in Moscow

France

François Hollande on his phone. Photograph: Ruet Stephane/Story Box Photo/Rex

The French president, François Hollande, is inseparable from his iPhone 5. He is reported to be in constant contact via text messages with his girlfriend Julie Gayet. But the presidential iPhone is supposed to be for personal use only.

Even before the Edward Snowden revelations about the US National Security Agency spying on French citizens, which forced government ministers to abandon smartphones and tablets for official use from last August, the French head of state was given an ultra-secure Teorem phone with encryption capabilities. But Hollande's predecessor, Nicolas Sarkozy, found the Teorem phone cumbersome, and refused to use it because it took 30 seconds to dial a connection, which "took too long for him", according to an aide. Sarkozy, who had a BlackBerry addiction, did not seem too worried about cybersecurity in his early days as president: he was photographed handing his mobile to Vladimir Putin at the 2007 G8 summit in Heiligendamm as they shared a phone call.

These days, the former president has become more circumspect. In order to (unsuccessfully) avoid phone taps, he bought a new mobile under the borrowed name of Paul Bismuth. The real Paul Bismuth is threatening legal action against the former president and his lawyer, a school friend of the French businessman who says his identity was stolen. Meanwhile, a French government memo advises ministerial phone users to adopt long passwords, which should be changed every six months, never to leave their phone unattended, particularly when travelling abroad, and never, ever, to use a smartphone for transmitting sensitive information, including in a text message. Anne Penketh in Paris

North Korea

Kim Jong-un pictured with what could be an HTC phone. Photograph: KNS/AFP

Speculation about Kim Jong-un's mobile phone use grew after he was photographed at a national security meeting in January 2013 with a smartphone that appeared to be made by the Taiwanese company HTC.

South Korean media said the North Korean leader probably used his handset to call members of his family and senior officials in the Workers' party of Korea. Kim is one of an estimated 2 million mobile phone users among North Korea's 25 million people. The country markets handsets as its own, but they are all made in China and rebadged with local brand names, according to Martyn Williams, who runs the North Korea Tech blog. Foreign models are also popular, but expensive. Use of mobiles in the North is confined to officials and their families, wealthy residents of the capital, Pyongyang, and, increasingly, businesspeople and traders with ties to China. Most phones run on the domestic 3G cellular service Koryolink, a joint venture between Egypt's Orascom Telecom and North Korea's Ministry of Posts and Telecommunications, although users near China can pick up a signal from carriers across the border.

North Korean subscribers are not permitted to access the internet via mobile phone – only to make calls and send texts inside the country. There is no international access. Foreign residents can use mobiles to communicate among themselves and make overseas calls, but not to contact local North Koreans, Williams said. Justin McCurry in Tokyo

Italy

Italy's prime minister, Matteo Renzi, is more than just an iPhone user – he is an Apple devotee who once had himself photographed beside the sign at the entrance to the company's headquarters. When Steve Jobs died, Renzi wrote a tribute to him on his Facebook page, calling him "the Leonardo da Vinci of our time".

Renzi has used his iPhone to send text messages of more than one sort. In 2012, when he first campaigned for the leadership of the centre-left Democratic party, promising to rottamare (demolish) the old leadership, he had a cover made for his smartphone that bore the slogan "Keep calm and rottama". John Hooper in Rome