We developed and tested an evidence-based mobile application designed to support families in using functional assessment-based intervention strategies with their young children with disabilities and challenging behaviors in home settings. Five families participated in the study. We utilized a multiple-probe across participants design to examine the effects of the FBSApp on parents' use of intervention strategies and childrens' use of challenging behaviors and replacement behaviors. We adapted our procedures to include individualized coaching to provide meaningful and effective support after the onset of the COVID-19 pandemic. A functional relation was not identified between access to FBSApp and caregiver use of strategies; however, the addition of coaching did lead to increased strategy use for two of four caregivers. A functional relation was identified between the use of the FBSApp plus coaching and CB. Families reported the app and coaching procedures favorably. We found that responsive, family-centered research CAN be conducted in spite of significant history events, and that mobile apps and virtual meeting platforms can be an accessible and efficient method for supporting families. The use of single case design allowed for flexible, yet methodologically sound procedures. More work is needed examining effective and efficient virtual supports for families.