Information and Communication Technology interventions have the potential to improve outcomes in health and other development sectors in low-income settings. Large-scale impact, however, remains the central challenge for the HCI4D community as significant and diverse resources are typically required to scale such interventions beyond the pilot stage. In contrast, voice-based entertainment services accessible over simple phones, designed for similarly low-income, low-literate populations manage to scale 'virally' to tens of thousands of users with little to no advertising cost. Our study compares the outcomes of using voice-based entertainment to spread a maternal-health hotline against conventional advertisement channels including paper flyers, posters, radio, TV, social media and robocalls. Through an 11-week deployment in Pakistan where the hotline reached 21,770 users over 32,625 calls, we find that the entertainment service outperformed other channels on all popular user acquisition metrics, with the exception of robocalls, which lead in terms of spread.

Information dissemination using automated phone calls allows reaching low-literate and tech-naive populations. Open challenges include rapid verification of expected knowledge gaps in the community, dissemination of specific information to address these gaps, and follow-up measurement of knowledge retention. We report Sawaal, a voice-based telephone service that uses audio-quizzes to address these challenges. Sawaal allows its open community of users to post and attempt multiple-choice questions and to vote and comment on them. Sawaal spreads virally as users challenge friends to quiz competitions. Administrator-posted questions allow confirming specific knowledge gaps, spreading correct information and measuring knowledge retention via rephrased, repeated questions. In 14 weeks and with no advertisement, Sawaal reached 3,433 users (120,119 calls) in Pakistan, who contributed 13,276 questions that were attempted 455,158 times by 2,027 users. Knowledge retention remained significant for up to two weeks. Surveys revealed that 71% of the mostly low-literate, young, male users were blind.

Speech is more natural than text for a large part of the world including hard-to-reach populations (low-literate, poor, tech-novice, visually-impaired, marginalized) and oral cultures. Voice-based services over simple mobile phones are effective means to provide orality-driven social connectivity to such populations. We present Baang, a versatile and inclusive voice-based social platform that allows audio content creation and sharing among its open community of users. Within 8 months, Baang spread virally to 10,721 users (69% of them blind) who participated in 269,468 calls and shared their thoughts via 44,178 audio-posts, 343,542 votes, 124,389 audio-comments and 94,864 shares. We show that the ability to vote, comment and share leads to viral spread, deeper engagement, longer retention and emergence of true dialog among participants. Beyond connectivity, Baang provides its users with a voice and a social identity as well as means to share information and get community support.