A GRXML developer designs and implements voice recognition systems using the Grammar Specification Language (GRXML). They create grammars to define the specific words, phrases, and patterns a voice system can understand. This involves understanding the syntax and semantics of GRXML, structuring XML documents, and defining voice commands. They also debug and optimize these systems to improve accuracy and efficiency. They often work closely with other developers and stakeholders to integrate voice recognition features into larger software systems. Their work is essential in developing applications like virtual assistants, automated phone systems, and accessibility features.