D2A is an open-source smartphone-based survey tool developed to support household-level nutrition data collection in rural Kenya. Deployed through KoboToolbox, the app enabled caregivers to self-collect Family MUAC measurements and report household-level factors associated with child undernutrition. Designed for accessibility, D2A included multilingual questionnaires in English, Swahili, and Pökoot, audio-assisted navigation for non-literate users, culturally appropriate visual prompts, and simple mobile workflows. The tool was tested in a seven-month pilot with 180 households in West Pokot County, Kenya. D2A demonstrated that smartphone-based household data collection can complement conventional survey systems, reduce costs, and increase resilience during periods when face-to-face data collection is difficult, including during crises such as COVID-19.