A quick and dirty way to attach "DebugView++.exe" to a window handle. The code makes a whole bunch of assumptions and has a lot of ugliness but it is so far serving my purpose so be nice :D

EmbeddedDebugView.cs

using System;
using System.ComponentModel;
using System.Diagnostics;
using System.IO;
using System.Runtime.InteropServices;

namespace Fushnisoft.Utils
{
    internal class EmbeddedDebugView
    {
        private static IntPtr _dbgViewWin = IntPtr.Zero;
        private static BackgroundWorker _bw = new BackgroundWorker();
        private static IntPtr _handle = IntPtr.Zero;

        [DllImport("user32.dll")]
        static extern IntPtr SetParent(IntPtr hWndChild, IntPtr hWndNewParent);
        [DllImport("user32.dll")]
        static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);
        [DllImport("user32.dll")]
        static extern bool MoveWindow(IntPtr Handle, int x, int y, int w, int h, bool repaint);
        [DllImport("user32.dll")]
        static extern bool PostMessage(IntPtr hWnd, uint Msg, Int32 wParam, Int32 lParam);
        [DllImport("user32.dll", SetLastError = true)]
        static extern bool GetWindowRect(IntPtr hWnd, out RECT lpRect);
        [DllImport("user32.dll")]
        static extern bool InvalidateRect(IntPtr hWnd, IntPtr lpRect, bool bErase);

        [StructLayout(LayoutKind.Sequential)]
        public struct RECT
        {
            public int Left;
            public int Top;
            public int Right;
            public int Bottom;
        }
        // Constant values were found in the "windows.h" header file.
        private const int WM_ACTIVATEAPP = 0x001C,
                          GWL_STYLE = -16,
                          WM_CLOSE = 0x10;

        public static class WindowStyles
        {
            public static readonly Int32
            WS_BORDER = 0x00800000,
            WS_CAPTION = 0x00C00000,
            WS_CHILD = 0x40000000,
            WS_CHILDWINDOW = 0x40000000,
            WS_CLIPCHILDREN = 0x02000000,
            WS_CLIPSIBLINGS = 0x04000000,
            WS_DISABLED = 0x08000000,
            WS_DLGFRAME = 0x00400000,
            WS_GROUP = 0x00020000,
            WS_HSCROLL = 0x00100000,
            WS_ICONIC = 0x20000000,
            WS_MAXIMIZE = 0x01000000,
            WS_MAXIMIZEBOX = 0x00010000,
            WS_MINIMIZE = 0x20000000,
            WS_MINIMIZEBOX = 0x00020000,
            WS_OVERLAPPED = 0x00000000,
            WS_OVERLAPPEDWINDOW = WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX,
            WS_POPUP = unchecked((int)0x80000000),
            WS_POPUPWINDOW = WS_POPUP | WS_BORDER | WS_SYSMENU,
            WS_SIZEBOX = 0x00040000,
            WS_SYSMENU = 0x00080000,
            WS_TABSTOP = 0x00010000,
            WS_THICKFRAME = 0x00040000,
            WS_TILED = 0x00000000,
            WS_TILEDWINDOW = WS_OVERLAPPED | WS_CAPTION | WS_SYSMENU | WS_THICKFRAME | WS_MINIMIZEBOX | WS_MAXIMIZEBOX,
            WS_VISIBLE = 0x10000000,
            WS_VSCROLL = 0x00200000;
        }

        internal static void Resize()
        {
            if (_dbgViewWin != IntPtr.Zero && _handle != IntPtr.Zero)
            {
                RECT rect = new RECT();
                GetWindowRect(_handle, out rect);
                MoveWindow(_dbgViewWin, 0, 0, rect.Right - rect.Left, rect.Bottom - rect.Top, true);
                InvalidateRect(_handle, IntPtr.Zero, true);
            }
        }

        internal static void Init(int handle)
        {
            _handle = new IntPtr(handle);
            _bw.DoWork += new DoWorkEventHandler(bw_DoWork);
            _bw.RunWorkerCompleted += new RunWorkerCompletedEventHandler(bw_RunWorkerCompleted);
            _bw.RunWorkerAsync();
        }

        private static void bw_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            if (e.Result != null)
            {
                _dbgViewWin = (IntPtr)e.Result;
                SetParent(_dbgViewWin, _handle);

                // Remove border and whatnot
                SetWindowLong(_dbgViewWin, GWL_STYLE, WindowStyles.WS_VISIBLE);

                // Move the window to overlay it on this window
                RECT rect = new RECT();
                GetWindowRect(_handle, out rect);
                MoveWindow(_dbgViewWin, 0, 0, rect.Right - rect.Left, rect.Bottom - rect.Top, true);
            }

        }

        private static void bw_DoWork(object sender, DoWorkEventArgs e)
        {
            string debugViewPath = "DebugView++.exe";
            if (debugViewPath != "" && File.Exists(debugViewPath) == true)
            {
                Process p = null;
                Process[] processes = Process.GetProcessesByName(Path.GetFileNameWithoutExtension(debugViewPath));
                if (processes.Length > 0)
                {
                    p = processes[0];
                    if (p.MainWindowHandle == IntPtr.Zero)
                    {
                        p.Kill();
                        p = null;
                    }
                }
                if (p == null)
                {
                    p = Process.Start(debugViewPath, "/f");
                }
                p.WaitForInputIdle();
                e.Result = p.MainWindowHandle;
            }
        }

        internal static void Destroy()
        {
            // Stop the application
            if (_dbgViewWin != IntPtr.Zero)
            {
                // Post a close message
                PostMessage(_dbgViewWin, WM_CLOSE, 0, 0);

                // Delay for it to get the message
                System.Threading.Thread.Sleep(1000);

                // Clear internal handle
                _dbgViewWin = IntPtr.Zero;
            }
        }
    }
}