While the Hindi typing features in Hindi Kalam are much similar to the popular Quillpad [read review], one feature that simply rocks in HindiKalam is the Hindi Spell Checker - a a big help when you are unable to form those complex Hindi words using any permutation of English characters.
Hindi Kalam has this additional feature where you can also mix text from any other language like English, French or even Chinese. Just enclose the text inside square parenthesis and HindiKalam would skip converting that to Hindi.
Though Quillpad lets you type in most Indian languages, Hindi Kalam, as the name suggests, is limited to only Hindi.
Hindi Kalam - Writing Hindi was never so easy
Thanks Devashish Fuloria for the tip who writes "The best thing is that it works according to the QWERTY keyboard making hindi writing very easy for rare users like me."