This chapter presents the integration of hardware and open-source software to build a low-cost (US$100) and high-speed eye tracker. With minor modifications of PlayStation 3 Eye (PS3 Eye) camera as the main hardware component and the proper coding adjustments in software interface to CL Eye Platform Driver, offered by open-source Code Laboratories, our low-cost eye tracker runs at the speed of 187 frames per second (fps) in 320 × 240 resolution, which is at least three times faster than the ordinary low-cost eye trackers usually running between 30 and 60 fps. We have also developed four application programs, which are ISO 9249-Part 9, Gaze Replay, Heat Map, and the Areas of Interest (AOI). Our design is then compared with the low-cost KSL-240 and commercially available high-price (over US$5,000) Tobii under ISO 9249-Part 9 eye-tracking test. The test performance favored ours in terms of response time and correct response rate.