Currently, numerous mobile health (mHealth) interventions are being developed across the globe to help improve public health outcomes. Earlier this year, our three-person team of Masters of Public Health students came up with a teen pregnancy prevention and Sexually Transmitted Infections (STI) protection mobile application (app) idea and presented it at the 2013 University of North Carolina (UNC) Science Expo event in Chapel Hill. Based on a review of evidence-based mHealth interventions, theories for changing teen health behavior, and the feedback from the first phase of the project, I have developed a process for development and testing of the mobile app with the ultimate goal of reducing teen pregnancy and Sexually Transmitted Infections in North Carolina. This paper documents the implementation and formative development of the Let's Talk About It mobile app intended to bring teen health resources to young people's fingertips. This process includes project management, measurement and evaluation, launch and marketing, and a plan for scale-up and sustainability. The strengths of this process are the involvement of the target audience and teen health experts in the development stages and the use of continuous evaluation methods to refine the app. The risks include the time required, unexpected financial costs, and potential competition.