Due to the radio range of the network; suspicious transmission; unattended nature; and easier access; Wireless Sensor Networks are vulnerable to malicious users and physical attacks. Hence security is a must in these cases. The development of a WSN for a secured temperature measurement system could be a feasible answer to these issues. The temperature signals are collected by sensors and transmitted to an Advanced RISC Microprocessor (ARM) via Wireless Fidelity (Wi-Fi) technology, which has been proven to transfer data accurately and reliably. The data is then stored in memory that is controlled by the microprocessor. The functionality is created using an ARM 9-based Samsung S3C2440 Controller with the Linux operating system. The security system is incorporated using the host MCUs and the temperature values are converted to digital form using the ARM processor's ADC (S3C2440). The processor is connected to the console terminal through UART, which sends data to the system on a regular basis with security data being monitored and transferred to other Wi-Fi-equipped devices through a USB-based Wi-Fi module, and the temperature readings are continuously monitored via this wireless sensor network. We perform the validation of our study through MATLAB simulations. Through MATLAB simulations we measure the total energy dissipated, throughput, and the lifetime of the sensor nodes. Overall, in this research, we develop an improved security in WSN system with application in ARM controller based secured temperature monitoring system. This paper paves a direction towards further research in physical security in Wireless Sensor Networks.