We are in the midst of a global health tragedy where over 3 million children in the developing world die annually before the age of 5 years(GBD 2013, Lancet, 2014) predominantly through infectious diseases as well as malnutrition and related disorders. A further 200 million children annually do not reach their developmental potential(Grantham, Lancet, 2007). A major challenge in diagnosing and treating these children in the developing world lies in the paucity of options for objectively measuring the nutritional, infection, and inflammation status of the gastrointestinal tract. To overcome this challenge, we recently engineered a strain of bacteria that is capable of sensing, remembering, and reporting on the environment within the gastrointestinal tract of animals. These engineered bacteria can safely traverse the gastrointestinal tract, analogously to probiotics, and then be retrieved from feces, analyzed in the laboratory, and enable predictive therapeutic interventions. Our proposal focuses on further developing these engineered bacteria and comprehensively testing their safety and capacity to reveal clinically-meaningful and therapeutically-actionable information. In the future, our technology could be deployed throughout the world, in a sustainable and scalable fashion, and aid in improving child health and wellbeing in both the developed and developing worlds.