I can read Bangla scripts in my cell phone via the opera mini browser but cannot write in Bangla. BanglaSMS has the solution for me as it offers an opensource program which can be downloaded and installed in my phone. From its website:
The software is self-contained. Just install it into your mobile phone and tell your friends to install it and there you go! All the GSM networks like Grameen Phone, Banglalink, Teletalk or Aktel users can use BanglaSMS to send sms in Bangla.The input system seems very easy. Can't wait to check it out.
Oh, by the way, you know what? On 21st February 2009, the great International Mother Language Day, we have released version 2.0.0 as open source (and of course completely free). So who knows, may be you or your friend will write codes to make it even better.