Tobii EyeXDotNet の Minimal Samples/MinimalGazeDataStream/Program.cs を改変して画面を見つめることでクリックできるようにしたコードです。

Program.cs

namespace MinimalGazeDataStream
{
    using EyeXFramework;
    using System;
    using System.Runtime.InteropServices;
    using Tobii.EyeX.Framework;

    public class NativeMethods
    {
        [System.Runtime.InteropServices.DllImportAttribute("user32.dll", EntryPoint = "SetCursorPos")]
        [return: System.Runtime.InteropServices.MarshalAsAttribute(System.Runtime.InteropServices.UnmanagedType.Bool)]
        public static extern bool SetCursorPos(int x, int y);

        [DllImport("user32.dll")]
        private static extern void SendInput(int nInputs, ref INPUT pInputs, int cbsize);

        public static void RightClick()
        {
            const int num = 2;
            INPUT[] inp = new INPUT[num];

            // マウスの右ボタンを押す
            inp[0].type = INPUT_MOUSE;
            inp[0].mi.dwFlags = MOUSEEVENTF_RIGHTDOWN;
            inp[0].mi.dx = 0;
            inp[0].mi.dy = 0;
            inp[0].mi.mouseData = 0;
            inp[0].mi.dwExtraInfo = 0;
            inp[0].mi.time = 0;

            // マウスの右ボタンを離す
            inp[1].type = INPUT_MOUSE;
            inp[1].mi.dwFlags = MOUSEEVENTF_RIGHTUP;
            inp[1].mi.dx = 0;
            inp[1].mi.dy = 0;
            inp[1].mi.mouseData = 0;
            inp[1].mi.dwExtraInfo = 0;
            inp[1].mi.time = 0;

            SendInput(num, ref inp[0], Marshal.SizeOf(inp[0]));
        }

        public static void LeftClick()
        {
            const int num = 2;
            INPUT[] inp = new INPUT[num];

            // マウスの左ボタンを押す
            inp[0].type = INPUT_MOUSE;
            inp[0].mi.dwFlags = MOUSEEVENTF_LEFTDOWN;
            inp[0].mi.dx = 0;
            inp[0].mi.dy = 0;
            inp[0].mi.mouseData = 0;
            inp[0].mi.dwExtraInfo = 0;
            inp[0].mi.time = 0;

            // マウスの左ボタンを離す
            inp[1].type = INPUT_MOUSE;
            inp[1].mi.dwFlags = MOUSEEVENTF_LEFTUP;
            inp[1].mi.dx = 0;
            inp[1].mi.dy = 0;
            inp[1].mi.mouseData = 0;
            inp[1].mi.dwExtraInfo = 0;
            inp[1].mi.time = 0;

            SendInput(num, ref inp[0], Marshal.SizeOf(inp[0]));
        }

        private const int INPUT_MOUSE = 0;                  // マウスイベント

        private const int MOUSEEVENTF_MOVE = 0x1;           // マウスを移動する
        private const int MOUSEEVENTF_ABSOLUTE = 0x8000;    // 絶対座標指定
        private const int MOUSEEVENTF_LEFTDOWN = 0x2;       // 左　ボタンを押す
        private const int MOUSEEVENTF_LEFTUP = 0x4;         // 左　ボタンを離す
        private const int MOUSEEVENTF_RIGHTDOWN = 0x8;      // 右　ボタンを押す
        private const int MOUSEEVENTF_RIGHTUP = 0x10;       // 右　ボタンを離す

        [StructLayout(LayoutKind.Explicit)]
        private struct INPUT
        {
            [FieldOffset(0)]
            public int type;
            [FieldOffset(4)]
            public MOUSEINPUT mi;
        };

        // マウスイベント(mouse_eventの引数と同様のデータ)
        [StructLayout(LayoutKind.Sequential)]
        private struct MOUSEINPUT
        {
            public int dx;
            public int dy;
            public int mouseData;
            public int dwFlags;
            public int time;
            public int dwExtraInfo;
        };
    }
    public static class Program
    {
        public static void Main(string[] args)
        {
            int xx = 0;
            int yy = 0;

            int x2 = 0;
            int y2 = 0;
            // Initialize the EyeX host.
            using (var eyeXHost = new EyeXHost())
            {
                eyeXHost.Init();

                using (var lightlyFilteredGazeDataStream = eyeXHost.CreateDataStream(new GazePointDataStream(GazePointDataMode.LightlyFiltered)))
                {
                    // Write the data to the console.
                    lightlyFilteredGazeDataStream.Next += (s, e) =>
                    {
                        Console.WriteLine("Gaze point at ({0:0.0}, {1:0.0}) @{2:0}", e.X, e.Y, e.Timestamp);
                        xx =(int) ((xx * 10 + e.X) / 11);
                        yy = (int)((yy * 10 + e.Y) / 11);
                        x2 = (int)((x2 * 20 + xx) / 21);
                        y2 = (int)((y2 * 20 + yy) / 21);

                        System.Windows.Forms.Cursor.Position = new System.Drawing.Point((int)xx, (int)yy);

                        if (Math.Abs(xx - x2) < 30 && Math.Abs(yy - y2) < 30)
                        {
                            NativeMethods.LeftClick();
                            x2 = 0;
                            y2 = 0;
                        }
                    };
                    // Let it run until a key is pressed.
                    Console.WriteLine("Listening for gaze data, press any key to exit...");
                    Console.In.Read();
                }
            }
        }
    }
}