Apple's iPhone was named invention of the year in 2007 by Time magazine. It is considered one of the greatest gadgets of all time.
One of the iPhone's biggest innovations was the introduction of the App Store, which allowed users to download small programs - some for cash and some for free - that added functionality to the device.
Since their introduction, more than 2 billion apps have been downloaded worldwide.
The phone has also become popular with teenagers in Hong Kong and now that outside vendors can submit their applications to the store, the supply and demand for better apps is growing. This was an opportunity that Ivan Wan Sai-hong, who studied computer science, could not miss. Last year, he quit his job in television production to become a freelance app developer.
'I had an interest in the media so I took a job in television after graduating. But developing iPhone apps allows me to make use of my knowledge in computers to develop skills in new areas.'
The cost of entry to the store as a would-be developer is fairly low for those short of capital. 'The only cost is a US$99 annual registration fee which is paid to Apple. (If accepted) apps will be put on to the store for downloading. I will share the profit of the download fee with Apple.'
Wan's first app - the hell bank note - has been downloaded more than 500 times since its release in December last year. At a cost of US$1.99, 70 per cent of the profit goes to 29-year-old Wan and the remainder to Apple.
Another source of income for Wan is helping companies develop apps. The charges depend on the complexity of the apps.
'At the moment, I'm talking with a food and beverage company about the development of an app to help users find branches and inform them of the latest dishes and discounts,' he said, adding that it will eventually be available as a free download on the store.
Wan said in the United States many corporates had begun to use iPhone apps to a promotional tool and the trend was just starting to take off in Hong Kong.
'In the US, there are apps that help users find cafes, restaurants and stores. Clothing stores had apps which help shoppers check out the availability of products and different sizes. Even singer Britney Spears has an app that allows users to download music and news,' he said.
Wan predicts that the use of apps can only grow. 'They are a whole new platform in marketing. More and more companies will want to make use of them to promote their products and services. Just as every company has its own website, every company will have its own apps.'
According to Wan, an app developer must be knowledgeable in programming and have a good marketing sense. 'Aside from hard computer skills, a developer needs to be aware of market trends and know how to help clients promote their products,' he said.