diff --git a/desktoppackage/contents/activitymanager/ActivityItem.qml b/desktoppackage/contents/activitymanager/ActivityItem.qml
--- a/desktoppackage/contents/activitymanager/ActivityItem.qml
+++ b/desktoppackage/contents/activitymanager/ActivityItem.qml
@@ -24,6 +24,7 @@
 
     property alias title       : title.text
     property alias icon        : icon.source
+    property alias hasWindows  : hasWindowsIndicator.visible
 
     z : current  ? 10 :
         selected ?  5 : 0
@@ -206,12 +207,10 @@
             }
         }
 
-        Item {
+        Column {
             id: statsBar
 
-            height: lastUsedDate.height +
-                 //     stats.height +
-                        units.smallSpacing
+            height: childrenRect.height + units.smallSpacing
 
             anchors {
                 bottom : controlBar.top
@@ -223,25 +222,25 @@
                 bottomMargin : units.smallSpacing
             }
 
+            PlasmaCore.IconItem {
+                id      : hasWindowsIndicator
+                source  : "window-duplicate"
+                width   : 16
+                height  : width
+                opacity : .6
+                visible : false
+            }
+
             Text {
                 id: lastUsedDate
 
                 color   : "white"
                 elide   : Text.ElideRight
                 opacity : .6
 
-                // text: root.current ?
-                //         i18nd("plasma_shell_org.kde.plasma.desktop", "Currently being used") :
-                //         ActivitySwitcher.Backend.lastTimeUsedString(root.activityId)
                 text: root.current ?
                         i18nd("plasma_shell_org.kde.plasma.desktop", "Currently being used") :
                         model.lastTimeUsedString
-
-                anchors {
-                    top   : parent.top
-                    left  : parent.left
-                    right : parent.right
-                }
             }
 
             // Text {
diff --git a/desktoppackage/contents/activitymanager/ActivityList.qml b/desktoppackage/contents/activitymanager/ActivityList.qml
--- a/desktoppackage/contents/activitymanager/ActivityList.qml
+++ b/desktoppackage/contents/activitymanager/ActivityList.qml
@@ -131,6 +131,7 @@
                 icon         : model.iconSource
                 background   : model.background
                 current      : model.isCurrent
+                hasWindows   : model.hasWindows
                 innerPadding : 2 * units.smallSpacing
                 stoppable    : activitiesList.count > 1
 
diff --git a/imports/activitymanager/CMakeLists.txt b/imports/activitymanager/CMakeLists.txt
--- a/imports/activitymanager/CMakeLists.txt
+++ b/imports/activitymanager/CMakeLists.txt
@@ -9,6 +9,7 @@
 find_package (KF5GuiAddons    ${KF5_DEP_VERSION} CONFIG REQUIRED)
 find_package (KF5KIO          ${KF5_DEP_VERSION} CONFIG REQUIRED)
 find_package (KF5Activities   ${KF5_DEP_VERSION} CONFIG REQUIRED)
+find_package (KF5WindowSystem ${KF5_DEP_VERSION} CONFIG REQUIRED)
 
 find_package (X11)
 set_package_properties (
@@ -44,6 +45,7 @@
    KF5::GuiAddons
    KF5::KIOCore
    KF5::KIOWidgets
+   KF5::WindowSystem
    ${X11_X11_LIB}
    )
 
diff --git a/imports/activitymanager/sortedactivitiesmodel.h b/imports/activitymanager/sortedactivitiesmodel.h
--- a/imports/activitymanager/sortedactivitiesmodel.h
+++ b/imports/activitymanager/sortedactivitiesmodel.h
@@ -22,12 +22,26 @@
 
 // Qt
 #include <QSortFilterProxyModel>
+#include <QWidgetList> //For WId
 
+// KDE
 #include <KActivities/Consumer>
 #include <KActivities/Info>
 
+// TODO: Remove after 5.6
 #include "backport/switcheractivitiesmodel.h"
 
+#include <config-X11.h>
+
+#if HAVE_X11
+#include <netwm.h>
+#else
+namespace NET {
+    typedef int Properties;
+    typedef int Properties2;
+} // namespace NET
+#endif
+
 class SortedActivitiesModel : public QSortFilterProxyModel {
     Q_OBJECT
 
@@ -50,7 +64,9 @@
 
     enum AdditionalRoles {
         LastTimeUsed       = KActivitiesBackport::ActivitiesModel::UserRole,
-        LastTimeUsedString = KActivitiesBackport::ActivitiesModel::UserRole + 1
+        LastTimeUsedString = KActivitiesBackport::ActivitiesModel::UserRole + 1,
+        WindowCount        = KActivitiesBackport::ActivitiesModel::UserRole + 2,
+        HasWindows         = KActivitiesBackport::ActivitiesModel::UserRole + 3
     };
 
 public Q_SLOTS:
@@ -64,10 +80,15 @@
     void onCurrentActivityChanged(const QString &currentActivity);
 
     QString activityIdForRow(int row) const;
+    QString activityIdForIndex(const QModelIndex &index) const;
     int rowForActivityId(const QString &activity) const;
 
     void rowChanged(int row, const QVector<int> &roles);
 
+    void onWindowAdded(WId window);
+    void onWindowRemoved(WId window);
+    void onWindowChanged(WId window, NET::Properties properties, NET::Properties2 properties2);
+
 Q_SIGNALS:
     void sortByLastUsedTimeChanged(bool sortByLastUsedTime);
     void inhibitUpdatesChanged(bool inhibitUpdates);
@@ -80,6 +101,12 @@
 
     KActivitiesBackport::ActivitiesModel *m_activitiesModel;
     KActivities::Consumer *m_activities;
+
+    QHash<QString, QVector<WId>> m_activitiesWindows;
+
+#if HAVE_X11
+    bool m_isOnX11;
+#endif
 };
 
 #endif // SORTED_ACTIVITY_MODEL
diff --git a/imports/activitymanager/sortedactivitiesmodel.cpp b/imports/activitymanager/sortedactivitiesmodel.cpp
--- a/imports/activitymanager/sortedactivitiesmodel.cpp
+++ b/imports/activitymanager/sortedactivitiesmodel.cpp
@@ -22,14 +22,22 @@
 
 // Qt
 #include <QColor>
+#include <QObject>
 
 // KDE
 #include <KConfig>
 #include <KConfigGroup>
 #include <KDirWatch>
 #include <KLocalizedString>
 #include <KActivities/Consumer>
 
+#define KWINDOWSYSTEM_NO_DEPRECATED
+
+#if HAVE_X11
+#include <KWindowSystem>
+#include <QX11Info>
+#endif
+
 namespace {
 
     class BackgroundCache {
@@ -171,14 +179,43 @@
     , m_sortByLastUsedTime(true)
     , m_activitiesModel(new KActivitiesBackport::ActivitiesModel(states, this))
     , m_activities(new KActivities::Consumer(this))
+#if HAVE_X11
+    , m_isOnX11(QX11Info::isPlatformX11())
+#endif
 {
     setSourceModel(m_activitiesModel);
 
     setDynamicSortFilter(true);
     setSortRole(LastTimeUsed);
     sort(0, Qt::DescendingOrder);
 
     backgrounds().subscribe(this);
+
+
+#if HAVE_X11
+    if (m_isOnX11) {
+        const QList<WId> windows = KWindowSystem::stackingOrder();
+
+        for (const auto& window: windows) {
+            KWindowInfo info(window, NET::WMVisibleName, NET::WM2Activities);
+            const QStringList activities = info.activities();
+
+            if (activities.isEmpty() || activities.contains("00000000-0000-0000-0000-000000000000")) continue;
+
+            for (const auto& activity: activities) {
+                m_activitiesWindows[activity] << window;
+            }
+        }
+
+        connect(KWindowSystem::self(), &KWindowSystem::windowAdded,
+                this,                  &SortedActivitiesModel::onWindowAdded);
+        connect(KWindowSystem::self(), &KWindowSystem::windowRemoved,
+                this,                  &SortedActivitiesModel::onWindowRemoved);
+        connect(KWindowSystem::self(), SIGNAL(windowChanged(WId, NET::Properties, NET::Properties2)),
+                this,                  SLOT(onWindowChanged(WId, NET::Properties, NET::Properties2)));
+    }
+#endif
+
 }
 
 SortedActivitiesModel::~SortedActivitiesModel()
@@ -260,21 +297,21 @@
 
     roleNames[LastTimeUsed]       = "lastTimeUsed";
     roleNames[LastTimeUsedString] = "lastTimeUsedString";
+    roleNames[WindowCount]        = "windowCount";
+    roleNames[HasWindows]         = "hasWindows";
 
     return roleNames;
 }
 
 QVariant SortedActivitiesModel::data(const QModelIndex &index, int role) const
 {
     if (role == KActivitiesBackport::ActivitiesModel::ActivityBackground) {
-        const auto activity =
-            QSortFilterProxyModel::data(index, Qt::UserRole).toString();
+        const auto activity = activityIdForIndex(index);
 
         return backgrounds().forActivity[activity];
 
     } else if (role == LastTimeUsed || role == LastTimeUsedString) {
-        const auto activity =
-            QSortFilterProxyModel::data(index, Qt::UserRole).toString();
+        const auto activity = activityIdForIndex(index);
 
         const auto time = lastUsedTime(activity);
 
@@ -305,14 +342,29 @@
 
         }
 
+    } else if (role == HasWindows || role == WindowCount) {
+        const auto activity = activityIdForIndex(index);
+
+        if (role == HasWindows) {
+            return (m_activitiesWindows[activity].size() > 0);
+        } else {
+            return m_activitiesWindows[activity].size();
+        }
+
+
     } else {
         return QSortFilterProxyModel::data(index, role);
     }
 }
 
+QString SortedActivitiesModel::activityIdForIndex(const QModelIndex &index) const
+{
+    return data(index, KActivitiesBackport::ActivitiesModel::ActivityId).toString();
+}
+
 QString SortedActivitiesModel::activityIdForRow(int row) const
 {
-    return data(index(row, 0), KActivitiesBackport::ActivitiesModel::ActivityId).toString();
+    return activityIdForIndex(index(row, 0));
 }
 
 int SortedActivitiesModel::rowForActivityId(const QString &activity) const
@@ -368,6 +420,59 @@
     }
 }
 
+void SortedActivitiesModel::onWindowAdded(WId window)
+{
+#if HAVE_X11
+    if (!m_isOnX11) return;
+
+    KWindowInfo info(window, 0, NET::WM2Activities);
+    const QStringList activities = info.activities();
+
+    if (activities.isEmpty() || activities.contains("00000000-0000-0000-0000-000000000000")) return;
+
+    for (const auto& activity: activities) {
+        if (!m_activitiesWindows[activity].contains(window)) {
+            m_activitiesWindows[activity] << window;
+
+            rowChanged(rowForActivityId(activity),
+                m_activitiesWindows.size() == 1
+                    ? QVector<int>{WindowCount, HasWindows}
+                    : QVector<int>{WindowCount});
+        }
+    }
+#endif
+}
+
+void SortedActivitiesModel::onWindowRemoved(WId window)
+{
+#if HAVE_X11
+    if (!m_isOnX11) return;
+
+    for (const auto& activity: m_activitiesWindows.keys()) {
+        if (m_activitiesWindows[activity].contains(window)) {
+            m_activitiesWindows[activity].removeAll(window);
+
+            rowChanged(rowForActivityId(activity),
+                m_activitiesWindows.size() == 0
+                    ? QVector<int>{WindowCount, HasWindows}
+                    : QVector<int>{WindowCount});
+        }
+    }
+#endif
+}
+
+void SortedActivitiesModel::onWindowChanged(WId window, NET::Properties properties, NET::Properties2 properties2)
+{
+#if HAVE_X11
+    if (!m_isOnX11) return;
+
+    if (properties2 & NET::WM2Activities) {
+        onWindowRemoved(window);
+        onWindowAdded(window);
+    }
+#endif
+}
+
 void SortedActivitiesModel::rowChanged(int row, const QVector<int> &roles)
 {
     if (row == -1) return;