Now there is an extension for chrome which enables Google transliteration on every text-box in all websites. I use this extension mostly for typing my first language in Gmail chat. For enabling this feature in Chrome browser, download and install Google Transliteration Service extension from Chrome Extension Gallery.
After installing, go to Chrome tools (Spanner Icon) > Extensions >Google Transliteration Service >Options and choose your your language and shortcut that to be used for enabling this feature. If you don't want to get changes in the appearance of text box, ignore other options in settings.
Screen Shot of Options page
After this step, enable transliteration on any page by typing the short cut. Now you can start typing the word in English and after each word, hitting space bar will convert the text automatically to your language.
Download (Chrome only)
