1. Yoolki Arabic Keyboard – Firefox Addon on Sony Xperia acro HD SO-03D/ U ST25 / ST25a / ST25i (Kumquat). Just open right click any text field and select "Write Arabic here" to write in Arabic using an English keyboard. The add-on can transliterate your English letters (ex: akala el waladou el touffA7ah to أَكَلَ الوَلَدُ التُفاحَة) or translate English to Arabic using Google translate. (ex: The boy ate the apple). Here this link :

http://supportscentre.com/free-download-yoolki-arabic-keyboard-firefox-addon-for-android.html

Note : You must have software requirement for addon : Fire fox mobile

2. Download here Arabic Language Pack for AnySoftKeyboard Sony Xperia acro HD SO-03D/ U ST25 / ST25a / ST25i (Kumquat). Here this link :

http://supportscentre.com/arabic-language-pack-for-anysoftkeyboard-version-20110127.html

3. Download Arabic soft Keyboard for Sony Xperia acro HD SO-03D/ U ST25 / ST25a / ST25i (Kumquat) Smartphone. Here this link :

http://supportscentre.com/arabic-soft-keyboard-abdullah-bahitham.html

4. Or find out more application from google play (android market) :

https://play.google.com/store/search?q=arabic+keyboard&c=apps