Index: /trunk/src/org/openstreetmap/josm/actions/ViewportFollowToggleAction.java
===================================================================
--- /trunk/src/org/openstreetmap/josm/actions/ViewportFollowToggleAction.java	(revision 15704)
+++ /trunk/src/org/openstreetmap/josm/actions/ViewportFollowToggleAction.java	(revision 15705)
@@ -9,4 +9,6 @@
 
 import org.openstreetmap.josm.actions.mapmode.DrawAction;
+import org.openstreetmap.josm.gui.Notification;
+import org.openstreetmap.josm.gui.util.GuiHelper;
 import org.openstreetmap.josm.tools.Shortcut;
 
@@ -37,4 +39,10 @@
         toggleSelectedState(e);
         DrawAction.VIEWPORT_FOLLOWING.put(isSelected());
+        if (!getShortcut().getKeyText().isEmpty()) {
+            String msg = isSelected()
+                    ? tr("Viewport following is enabled, press {0} to disable it", getShortcut().getKeyText())
+                    : tr("Viewport following is disabled");
+            GuiHelper.runInEDT(() -> new Notification(msg).show());
+        }
         notifySelectedState();
     }