Hi Hui-Shyong,
The X2-30 and X2-60 eye trackers are optimized for research and analysis. When doing research and analysis, gaze data is recorded with high accuracy and precision at a fixed frame rate (X2-30 provides gaze data at 30Hz, and X2-60 at 60Hz). Since the calculations are done after all the data has been collected there are different possibilities and requirements on the hardware, firmware and software than on the EyeX Controller, which is used for interaction, doing the calculations based on fewer data points in real-time.
The EyeX Controller together with the EyeX Engine enables great eye-gaze based interaction using less costly hardware components and no fixed frame rate. The EyeX Engine software uses a clever combination of real-time data filtering, information about the layout, behavior and size of the regions on the screens the user can interact with, and different user input, to decide what the user wants to do.
/Jenny