The use of phones is changing from landline phones to mobile phones. This change is not reflected in the IP PBX solutions available today. This report investigates how an extension can be developed to Cisco VoIP to reflect the change in phone usage. The solution, named Yink, is a scalable client-server system. The clients are mobile applications providing PBX functionality, and the server integrates the mobile phones with the existing Cisco VoIP system.