There's really no reason to rely on Memrise for this feature. It can be easily integrated and personally configured within your browser. Google provides a very useful set of input tools that work well with Memrise.
Google Input Tools[]
Google Input Tools for Windows is an input method editor which allows users to enter text in any of the supported languages using a Latin (English / QWERTY) keyboard. Users can type a word the way it sounds using Latin characters and Google Input Tools for Windows will convert the word to its native script. Available input tools include transliteration, IME, and on-screen keyboards.
Google Input Tools for Windows is currently available for 22 different languages: Amharic, Arabic, Bengali, Persian, Greek, Gujarati, Hebrew, Hindi, Kannada, Malayalam, Marathi, Nepali, Oriya, Punjabi, Russian, Sanskrit, Serbian, Sinhala, Tamil, Telugu, Tigrinya and Urdu.
Arabic Input Tools[]
http://memrise-users.wikia.com/wiki/Arabic_layout_(initial,_middle_and_end_characters)