The Mojo for Modbus application enables mobile field service personnel to monitor and control a wide variety of industrial devices based on the popular Modbus protocol. The package has unique features not previously available for mobile users, including multiple secure access layers and user-defined control limits and alarms. The target users for the software include field service personnel, engineers, and maintenance technicians. The software includes security layers and password access to restrict selective users' access on critical equipment to read-only, while granting authorized users full access. The package eliminates the need for laptops while enabling authorized users to monitor and control Modbus-compliant PLCs and other devices from a pocket-sized computer. The software also includes control limit definitions and alarms that reduce the time spent for field checks to a minimum. Server-based deployments are available for 5 or more users.