Added source code.

.gitignore

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+bin/
+*.user
+.vs/

App.config

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+<?xml version="1.0" encoding="utf-8"?>
+<configuration>
+    <configSections>
+        <sectionGroup name="userSettings" type="System.Configuration.UserSettingsGroup, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" >
+            <section name="Sandman.Properties.Settings" type="System.Configuration.ClientSettingsSection, System, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" allowExeDefinition="MachineToLocalUser" requirePermission="false" />
+        </sectionGroup>
+    </configSections>
+	<!--
+		Apparently WMC is in .NET 2.
+		.NET 4 changed how it loads legacy frameworks.
+		So we need this attribute.
+	-->
+	<startup useLegacyV2RuntimeActivationPolicy="true">
+		<supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.8" />
+	</startup>
+	<userSettings>
+        <Sandman.Properties.Settings>
+               <setting name="MinimumTimeBeforeNextRecording" serializeAs="String">
+                      <value>00:30:00</value>
+               </setting>
+               <setting name="DelayBeforeSuspending" serializeAs="String">
+                      <value>00:00:10</value>
+               </setting>
+               <setting name="TimeUserInactiveBeforeSuspending" serializeAs="String">
+                      <value>00:30:00</value>
+               </setting>
+               <setting name="DelayAfterResume" serializeAs="String">
+                      <value>00:10:00</value>
+               </setting>
+               <setting name="BlacklistedProcesses" serializeAs="String">
+                      <value>ehshell;epg123;epg123client;hdhr2mxf;epg123Transfer;WMC_Status;vlc</value>
+               </setting>
+               <setting name="DelayForElevatedProcess" serializeAs="String">
+                      <value>00:01:00</value>
+               </setting>
+        </Sandman.Properties.Settings>
+    </userSettings>
+</configuration>

App.xaml

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+<Application x:Class="Sandman.App"
+   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+   xmlns:local="clr-namespace:Sandman"
+   StartupUri="MainWindow.xaml"
+	ShutdownMode="OnExplicitShutdown"
+>
+    <Application.Resources>
+    </Application.Resources>
+</Application>

App.xaml.cs

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+using System.Windows;
+
+namespace Sandman
+{
+	/// <summary>
+	/// Interaction logic for App.xaml
+	/// </summary>
+	public partial class App : Application
+	{
+	}
+}

MainWindow.xaml

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+<Window x:Class="Sandman.MainWindow"
+   xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+   xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+   xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+   xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+   xmlns:local="clr-namespace:Sandman"
+   mc:Ignorable="d"
+   Title="Sandman" Width="600" Height="400"
+   Icon="/Sandman;component/Resources/weather_moon_half.png"
+   Loaded="Window_Loaded"
+	Closing="Window_Closing"
+>
+   <Grid>
+		<TextBox TextWrapping="Wrap" Text="{Binding ConsoleLog, Mode=OneWay}"
+			BorderThickness="0" IsReadOnly="True" IsReadOnlyCaretVisible="True" VerticalScrollBarVisibility="Visible" HorizontalScrollBarVisibility="Auto"
+		/>
+	</Grid>
+</Window>

MainWindow.xaml.cs

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+using System;
+using System.ComponentModel;
+using System.Diagnostics;
+using System.IO;
+using System.Text;
+using System.Threading;
+using System.Windows;
+
+namespace Sandman
+{
+	/// <summary>
+	/// Interaction logic for MainWindow.xaml
+	/// </summary>
+	public partial class MainWindow : Window, INotifyPropertyChanged
+	{
+		public static readonly string ExecutableFolder;
+		public StringBuilder ConsoleLog { get; set; } = new StringBuilder();
+
+		private readonly MyLibrary.NotificationIcon _notificationIcon = null;
+
+
+		static MainWindow()
+		{
+			var asm = System.Reflection.Assembly.GetEntryAssembly();
+			ExecutableFolder = Path.GetDirectoryName(asm.Location);
+		}
+		public MainWindow()
+		{
+			// remove original default trace listener
+			Trace.Listeners.Clear();
+
+			// form path to log file
+			string pathLog = Path.Combine(ExecutableFolder, "Sandman.log");
+
+			// add new default listener and set the filename
+			DefaultTraceListener listener = new DefaultTraceListener
+			{
+				LogFileName = pathLog
+			};
+			Trace.Listeners.Add(listener);
+			Trace.AutoFlush = true;
+
+			/*
+			 * Set up notification area icon
+			 */
+			_notificationIcon = new MyLibrary.NotificationIcon(this, Properties.Resources.Sandman, nameof(Sandman), new System.Windows.Forms.MenuItem[0]);
+
+			InitializeComponent();
+			DataContext = this;
+		}
+
+
+		private async void Window_Loaded(object sender, RoutedEventArgs e)
+		{
+			await WatchWMC.StartAsync(this).ConfigureAwait(continueOnCapturedContext: false);
+		}
+
+
+		private void Window_Closing(object sender, CancelEventArgs e)
+		{
+			if (_notificationIcon.ShouldClose())
+			{
+				Application.Current.Shutdown();
+				return;
+			}
+
+			e.Cancel = true;
+			Hide();
+			Trace.Flush();
+		}
+
+
+		public void WriteOutput(string s)
+		{
+			string timestampedMessage = $"[{DateTimeOffset.Now:yyyy-MM-dd HH:mm:ss}] (Thread {Thread.CurrentThread.ManagedThreadId:00}) {s}";
+			Trace.TraceInformation(timestampedMessage);
+			ConsoleLog.AppendLine(timestampedMessage);
+
+			RaisePropertyChanged(nameof(ConsoleLog));
+		}
+
+
+		// Boilerplate code
+		#region IRaisePropertyChanged
+
+		#region INotifyPropertyChanged
+
+		public event PropertyChangedEventHandler PropertyChanged;
+
+		#endregion INotifyPropertyChanged
+
+		public void RaisePropertyChanged(string propertyName)
+		{
+			PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
+		}
+
+		#endregion IRaisePropertyChanged
+	}
+}

NativeMethods.cs

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+using System;
+using System.Runtime.InteropServices;
+
+namespace Sandman
+{
+	public class NativeMethods
+	{
+		public static TimeSpan GetTimeSinceLastActivity()
+		{
+			LASTINPUTINFO lastInputInfo = LASTINPUTINFO.Create();
+			if (!GetLastInputInfo(ref lastInputInfo))
+			{
+				return TimeSpan.Zero;
+			}
+
+			// Even though it says "ticks," it's really milliseconds.
+			/// <see cref="https://docs.microsoft.com/en-us/dotnet/api/system.environment.tickcount"/>
+			uint msecEnvTicks = (uint)Environment.TickCount;
+			uint lastInputTick = lastInputInfo.dwTime;
+			uint idleTime = msecEnvTicks - lastInputTick;
+			return TimeSpan.FromMilliseconds(idleTime);
+		}
+
+
+		/// <see cref="https://www.pinvoke.net/default.aspx/Structures/LASTINPUTINFO.html"/>
+		[StructLayout(LayoutKind.Sequential)]
+		private struct LASTINPUTINFO
+		{
+			public static readonly int SizeOf = Marshal.SizeOf(typeof(LASTINPUTINFO));
+
+			[MarshalAs(UnmanagedType.U4)]
+			public UInt32 cbSize;
+			[MarshalAs(UnmanagedType.U4)]
+			public UInt32 dwTime;   // Even though it says "ticks," it's really milliseconds.
+
+			public static LASTINPUTINFO Create() => new LASTINPUTINFO()
+			{
+				cbSize = (uint)SizeOf,
+				dwTime = 0,
+			};
+		}
+
+		/// <see cref="https://www.pinvoke.net/default.aspx/user32.GetLastInputInfo"/>
+		/// <param name="plii"></param>
+		/// <returns></returns>
+		[DllImport("user32.dll")]
+		private static extern bool GetLastInputInfo(ref LASTINPUTINFO plii);
+	}
+}