A Kannel developer primarily focuses on developing, implementing, and maintaining systems using Kannel, an open-source WAP and SMS gateway. They design and develop SMS-based applications, manage SMS routing, and ensure the system's efficient performance. They may also create WAP push applications, handle troubleshooting and problem-solving tasks, and provide support for issues related to WAP and SMS gateways. Additionally, they might be involved in integrating Kannel with other systems or software, and they often work closely with other developers and stakeholders to meet specific project or application requirements. They also need to stay updated on new technological advancements in their field.