Some days ago it was quite difficult to write bangla on mobile but for the android market it become very easy already. i have Samsung galaxy tab and i recently just install mayabi keyborad and typing phontic bangla very easily.
How to install mayabi Keyboard on Android Mobile?
Go to market search for mayabi bangla keyboard. after searching it will show up on your phone apps list. just press and install. after successfully install go to phone settings choose language and keyboard as mayabi keyboard select input method is mayabi keyboard
Now you are ready to write bangla on your phone. go to any writing application such as Memo or Catch. and start typing bangla. you need to use phonetic typing
To write in Bangla, tap the key labeled Bangla. Now start writing using phonetic conventions. If you want to wite আমার সোনার বাংলা, type ‘amar sOnar bangla’ and that will be converted into Bangla text.
Note: I have tested this apps only on Samsung Galaxy Tab root . You must have update version of Samsung mobile to write bangla perfectly.