One of the biggest struggles researchers face when conducting trials is recruiting and retaining patients. These challenges have led drug developers to outsource their patient-recruitment-related needs, creating an opportunity for startups focused on this niche. Startups are aiming to increase patient retention by creating medication adherence and tracking technology, biometric monitoring devices, AI-powered direct observational therapy, and personalized platforms. This note provides an overview of startups that focus on clinical-trial recruitment and retention, the markets they face, and the technologies they provide.