An Angular and Ionic developer can provide services such as building and maintaining web and mobile applications using the Angular framework and the Ionic framework. This can include creating new features, debugging and troubleshooting issues, and optimizing performance. The developer may also be able to integrate the application with external APIs and services, as well as implement responsive design to ensure the application looks and functions well on a variety of devices and screen sizes. They may also be able to provide guidance on best practices for building scalable and maintainable applications using these technologies.