A CoreMotion developer designs and implements applications using Apple's Core Motion framework that allows access to motion and environment data from iOS devices. They capture and analyze data from accelerometers, gyroscopes, pedometers, and magnetometers to create features like health tracking, navigation, and physical gaming. They also optimize power usage and memory consumption, and ensure data accuracy. Their work facilitates the creation of intuitive, motion-based controls and features in apps, enhancing user experience. They collaborate with other developers, troubleshoot issues, and perform testing to ensure optimal performance.