The Garmin vivofit jr. 3 Kids Fitness Tracker in Disney The Little Mermaid design is an adjustable activity tracker designed for children. With a focus on running and jogging, this wearable computer from Garmin allows kids to track their physical activity while also incorporating the fun of Disney's The Little Mermaid theme. The tracker is adjustable in size to comfortably fit young users, making it a fun and practical tool for promoting fitness and healthy habits.