The widespread adoption of Internet of Things (IoT)-based smart home systems has led to increasing reliance on cloud-dependent architectures that require stable internet connectivity. However, such dependence restricts deployment in environments with limited or unreliable network infrastructure. This study presents the design, implementation, and performance evaluation of an offline-first smart home automation system based on Bluetooth communication and Android-based voice control. The system integrates a NodeMCU ESP8266 microcontroller, an HC-05 Bluetooth module, and a multi-channel relay interface to enable localized appliance control without internet dependency. A dual-mode interaction framework is implemented, supporting both manual control through a graphical user interface and voice-command input using speech recognition. System performance is evaluated in terms of response time, communication range, packet delivery success rate, power consumption, and operational stability. Experimental results indicate average response times of 0.3 s and 0.8 s for manual and voice-control modes, respectively, with stable communication achieved over a 10 m line-of-sight range. Packet delivery success rates of 98.0% and 94.5% were obtained under line-of-sight and obstructed indoor conditions, respectively, demonstrating reliable command execution in practical operating environments. The results demonstrate that the proposed offline-first architecture provides a robust, cost-effective, and infrastructure-independent solution for localized smart home automation, particularly in resource-constrained environments.