What should be done to create a full iOS app in tamil language?

I want to create an iOS application which consists of Tamil language. I see so many applications in appstore which is fully of tamil language. But, it is not a localized language in iPhone. So how can we achieve it? How are they developing a complete tamil application in iPhone? Thanks in advance :)

There's nothing special you need to do. Simply enter any text in your .xib (or programmatically) in Tamil using a font that has the Tamil characters, and it will be displayed in Tamil on all systems, regardless of their language setting. (In other words, it will not be localized to any other language.)