In 2020, there were 700 overdose deaths in San Francisco, which was more than double the number of COVID deaths. Though the proximal cause of death is Fentanyl, 60% of those who died were using methamphetamines, which means that many of those deaths may have been prevented by targeting stimulant use. UCSF Citywide serves nearly 2000 people annually with serious mental illness (SMI), homelessness, and institutionalization (long-term locked psychiatric hospitalization and incarceration). Over the last ten years, we have noted a steady rise in methamphetamine use and associated adverse outcomes in our client population, including worsened psychotic symptoms, increased likelihood of arrests or recidivism, increased social challenges (such as houselessness), and increased use of acute psychiatric services. Unlike many substance-use disorders, methamphetamine-use disorder (MUD) lacks an effective medication-based intervention. The only treatment with a clear evidence base is contingency management (CM). However, this treatment has not been widely used because of two challenges, (1) it has only been used experimentally because it financially rewards clients for reducing substance use, which brings up concerns about cost, sustainability, and diversion of funds, and (2) it is administratively complex to implement. The first challenge has been answered. The fact that California will launch a state-wide CM pilot through CalAIM and there is interest at the federal level to make CM reimbursable through public insurance indicates that CM will become a mainstream treatment. T A digital solution can answer the second challenge by using an app that would make CM more scalable by reducing the heavy administrative burden. We have obtained $1M philanthropic funding to develop an app to provide contingency management to our justice-involved clients who struggle with mental health challenges and substance use disorder. This project aims to (1) provide CM to reduce stimulant use, (2) increase digital literacy and access to aim for “digital belonging” for those at the margins of society, (3) support overall recovery goals through gamification and rewards, and (4) clarify implementation steps necessary to provide CM to this highly marginalized population successfully.