Health Alliance International (HAI) has supported the Ministry of Health in Timor-Leste to strengthen its maternal and newborn care services since 2004. In 2011 a USAID Child Survival grant funded a pilot project to implement and assess the effectiveness of mobile phones to improve the communication between midwives and the mostly rural pregnant woman they serve. The project is known as Liga Inan (Connecting Women) in the local language, or Mobile Moms. In addition to facilitating direct communication, a web-based platform sends text messages that are specific to the gestational stage of the woman's pregnancy. The effectiveness of the strategy will be evaluated via comparisons with a neighboring district. This paper discusses critical design issues that arose as the project unfolded. They included decisions related to existing patterns of cell phone use by rural women; the configuration of routine and emergency maternal care services in the health care system; the capacity of the local telecommunications system; local capacity in software development and support; specifications required of project phones; the selection, adaptation, review and pretesting of SMS messages; a range of issues around training of midwives in using and maintaining the system; and support needed to assure program quality in this innovative project. Effective resolution of these issues will be important in the design of any effort to use cell phones to improve health communication.