In this paper, we present the design, implementation, and deployment of a phone-based broadcasting system designed for reaching out to at-risk populations in urban India. We worked in collaboration with Pragati, a non-governmental organization dedicated to assisting Urban Sex Workers (USWs) in Bangalore, India, with the goal of improving Pragati’s outreach to the women they serve. We conducted ethnographic action research to understand and address the needs of Pragati and the lifestyles of USWs. Responding to the unique design constraints of the USW community such as specific privacy and timing constraints, a desire to remain invisible, and the unusually high rate of mobile phone use, we designed a phone-based broadcasting system for Pragati. We then deployed the system on four different occasions and application areas. We present the results and key findings from our study, and conclude with a discussion on how designing for particularly difficult cases such as USWs can shed new light on the design of mobile applications for the developing world in general, such as challenging ubiquity and phone numbers as identity.