Background: A common challenge within psychiatry and prevention science more broadly is the lack of effective, engaging, and scale-able mechanisms to deliver psycho-social interventions for children, especially beyond in-person therapeutic or school-based contexts. Although digital technology has the potential to address these issues, existing research on technologyenabled interventions for families remains limited. Objective: The aim of this pilot study was to examine the feasibility of in-situ deployments of a low-cost, bespoke prototype, which has been designed to support children's in-the-moment emotion regulation efforts. This prototype instantiates a novel intervention model that aims to address the existing limitations by delivering the intervention through an interactive object (a 'smart toy') sent home with the child, without any prior training necessary for either the child or their carer. This pilot study examined (i) the engagement and acceptability of the device in the homes during 1 week deployments; and (ii) qualitative indicators of emotion regulation effects, as reported by parents and children. Methods: In this qualitative study, ten families (altogether 11 children aged 6-10 years) were recruited from three underprivileged communities in the UK. The RA visited participants in their homes to give children the 'smart toy' and conduct a semi-structured interview with at least one parent from each family. Children were given the prototype, a discovery book, and a simple digital camera to keep at home for 7-8 days, after which we interviewed each child and their parent about their experience. Thematic analysis guided the identification and organisation of common themes and patterns across the dataset.In addition, the prototypes automatically logged every interaction with the toy throughout the week-long deployments. Results: Across all 10 families, parents and children reported that the 'smart toy' was incorporated into children's emotion regulation practices and engaged with naturally in moments children wanted to relax or calm down. Data suggests that children interacted with the toy throughout the duration of the deployment, found the experience enjoyable, and all requested to keep the toy longer. Child emotional connection to the toy-caring for its 'well-being'-appears to have driven this strong engagement. Parents reported satisfaction with and acceptability of the toy. Conclusions: This is the first known study investigation of the use of object-enabled intervention delivery to support emotion regulation in-situ. The strong engagement and qualitative indications of effects are promising -children were able to use the prototype without any training and incorporated it into their self-regulation practice during daily challenges. Future work is needed to extend this indicative data with efficacy studies examining the psychological efficacy of the proposed intervention. More broadly, our findings suggest the potential of technology-enabled shift in how prevention interventions are designed and del...