Sellinam is described as 'enables Tamil text input on mobile devices. It suports Tamil phonetic keyboard too. It was first developed in the year 2003 and subsequently launched for public usage in 2005 on Ponggal day' and is an app in the OS & Utilities category. There are three alternatives to Sellinam for a variety of platforms, including Android, Windows, iPad, iPhone and Mac. The best alternative is Keyman, which is free. Other great apps like Sellinam are Azhagi+ (AzhagiPlus) (Free) and PolyglotKeyboard (Free).
With keyboards for over 1000 languages, Keyman Desktop lets you type in your language even when Windows doesn't. You can even create your own custom keyboards with Keyman Developer 9.0. The free version offers 2 languages.
PolyglotKeyboard is an application for polyglots, for people, who need to type different languages (nearly) simultaneously. It allows using simple keyboard shortcuts for writing desired special characters found in different alphabets.