Child undernutrition remains one of the most devastating realities in many parts of the world. The use of mobile phone technology may offer innovative opportunities to tackle persistently high levels of child undernutrition. Despite the enthusiasm for using mobile phones for nutrition service delivery, a recent review found very few studies that critically assessed their application. A major shortcoming of the existing studies was that they were all based on small one-off pilot projects and integration into national nutrition strategies or programmes was minimal or non-existent. As a result of this lack of integration, the sustainability of mobile phone-based nutrition systems was generally low and most projects ceased to exist after the pilot. Together with World Vision Indonesia and World Vision Canada, we aim to address this evidence gap. We set out to rigorously evaluate the piloting of a mobile phone application for nutrition service delivery, including community-based growth monitoring and nutrition counselling.