It's a question of saturation. For example, in Hong Kong, the battle for the smartphone market was played out long ago. It has a remarkable penetration rate of 87 per cent, according to a study late last year by Flurry Analytics, which found only one other market - Singapore, at 92 per cent - where smartphones were more prevalent. Sweden, the United States, Britain, Australia and South Korea all hover around the 75 per cent mark, which makes them equally unappealing places to do business for mobile operators looking for big profits.

Apple and Google devices are too pricey for those in developing countries, so we are starting to see more basic smartphones dominate there. Take phones such as Nokia's 105, which has a colour screen, FM radio and a flashlight for a mere HK$150, or the Finnish firm's new 301, a bare-bones internet/e-mail smartphone costing just HK$650.

Lenovo's LePhone A586 - an Android gadget enabled with data storage system Baidu Cloud and voice unlock - sells for HK$1,264 on the mainland, compared to HK$5,588 for an iPhone 5.

High-end smartphones are packed with technology that potential customers in developing countries simply are not interested in: voice recognition, eye tracking and high-resolution photography are not must-haves. Besides, the clones are already out in force. In China, there are several iPhone 5 clone phones, normally based on Android, on sale for less than HK$700. In the long run, such phones are bound to be provided by mobile operators desperate for a share of such a huge market.

But in some respects, more expensive phones may save users money in the long run - especially when it comes to the cost of a phone call.

"Calling apps have made cheaper smartphones far more enticing by undercutting feature phones, offering longer-term savings and greater coverage in exchange for a slightly larger upfront cost," says Graeme Hutchinson, who runs Ghost Telecom, producer of free-calling app FooTalk.

Apps like these are designed to help users in developing countries take advantage of the growth of free or cheap Wi-fi zones, which attempt to "patch" gaps in mobile infrastructures.

It's all fuelling a more flexible and increasingly global outlook from mobile operators and app makers. "For operators, developed markets are at over-saturation point and we're seeing a reduction in new user take-up," says Hutchinson. "Operator growth, therefore, has to come from emerging and developing markets. With data services central to the future of mobile, operators' traditional geographical boundaries are disappearing and they are looking to global strategies that embrace the developing world."

On a recent visit to rural India, I saw how fast the mobile phone is penetrating even the most far-flung areas.

In a remote village on Bali Island, in West Bengal, there is no mains power, very few vehicles, and the nearest hospital is a 90-minute boat ride away. There is, however, a strong mobile signal from Vodafone India throughout and the mobile phone is ubiquitous. A basic handset costs about 600 rupees (HK$85) and can be recharged in the same small kiosks that sell air time. Most crucially, calls to anywhere in India cost a mere rupee per minute, which makes the medium instantly affordable to the 1.2 billion population.

"India's huge population used to be its biggest problem, but it's quickly becoming its biggest asset," a local NGO worker says. "One rupee per minute? It's unbelievable."

There's another aspect of developing countries' thirst for smartphones that makes the iPhone and even Google's Android unsuitable for the next billion users. Both are locked systems that require users to have an account with Apple or Google, in addition to paying their local mobile operators for air time and web access. In developing countries, where banking is far less common, this approach does not work.

"The current App store model present in the West, which requires consumer credit or debit card details, is not one that can be easily transferred across emerging markets," says Marco Veremis, chief executive of marketing technology company Upstream.

Veremis thinks the unique billing and marketing relationship that mobile network operators have with consumers in emerging markets put them in pole position - and not the likes of Apple.

A great example of all of these trends is Telefónica's plans for Latin America. The Spanish mobile operator - which has links with multinationals such as América Móvil, China Unicom, Deutsche Telekom and SingTel - isn't just moving its focus to markets such as Venezuela and Brazil, it's also bringing a new business model based on a brand new smartphone operating system called Firefox.

"Latin America is not being well-addressed by current offerings," says Dan Appelquist, the open web advocate at Telefónica Digital. "High-end smartphones are priced out of the reach of the vast majority of consumers and we see low-end Android devices offering a very poor experience."

Telefónica thinks Firefox - a completely open-source platform that essentially allows users to tweak, copy and distribute the software for free, can host any app and enables users to pay only the mobile operator - is far more suited to emerging markets than "walled garden" platforms.

Telefónica isn't alone; Lenovo and Baidu will soon be launching their cheap smartphones in Brazil, where penetration is a mere 14 per cent, while Nokia is heavily promoting its low-cost Windows smartphones in emerging nations - with a focus on India.

So are the likes of Apple and Google on the back foot? Samsung and Nokia top consumers' wish lists in emerging economies, followed only then by Apple, according to Upstream's 2013 Emerging Markets Mobile Attitudes report, which polled consumers in Brazil, India, Nigeria and Saudi Arabia on mobile data consumption and attitudes to mobile devices.

Although 16 per cent in those countries are willing to spend more than HK$3,500, the majority are looking for a smartphone for less than HK$775 to HK$2,300. It might be the most famous of the lot, but the iPhone in its current form isn't the future - and the winners will be the network operators, not smartphone makers.