This paper addresses effective artificial landmark based indoor localization technique for mobile robotics applications. In the proposed approach, QR-codes are strategically placed in the operating environment, attached to the ceiling; they are used as artificial landmarks for providing reference points to aid the robot localization. The vision processing, robot localization and navigation tasks are all carried out on an Android Smartphone mounted on the mobile robotic platform; by taking advantage of the computational power, the built-in sensing, and the communication capabilities of the Smartphone. The Smartphone detects and recognizes the QR-codes to calculate the approximate global location of the robot. The pixel coordinate information in the image of QR-code is also used to enhance the position estimate in the real-world environment. Furthermore, the QR-code orientation in the image view is used to calculate the mobile robot's heading direction. An NDI 3D optical tracking instrument is used for validation of the effectiveness and feasibility of the proposed method. This paper demonstrates successful implementation of the QR-code based localization strategy and the experimental evaluation of its performance in actual environment.