The computing for development community knows how to build user interfaces using qualitative methods for text illiterate users, especially on mobile devices. However, little work has been done specifically targeting Deaf users in developing regions who cannot access voice or text. This paper describes a multi-disciplinary collaboration towards iterative development of a mobile communication tool to support a Deaf person in understanding usage directions for medication dispensed at a pharmacy. We are improving usability and correctness of the user interface. The tool translates medicine instruction given in English text to Sign Language videos, which are relayed to a Deaf user on a mobile phone. Communication between pharmacists and Deaf patients were studied to extract relevant exchanges between the two users. We incorporated the common elements of these dialogues to represent content in a verifiable manner to ensure that the mobile tool relays the correct information to the Deaf user. Instructions are made available for a Deaf patient in signed language videos on a mobile device. A pharmacy setup was created to conduct trials of the tool with groups of end users, in order to collect usability data with recorded participant observation, questionnaires and focus group discussions. Subsequently, pre-recorded sign language videos, stored on a phone's memory card, were tested for correctness. Results of these two activities are presented and discussed in this paper, in preparation for a future trial in an actual pharmacy.