Actual project things

Assets/ViewFrustrumTrigger.cs

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+using UnityEngine;
+using System.Collections;
+
+public class ViewFrustrumTrigger : MonoBehaviour {
+    public Camera Camera;
+
+    public delegate void ViewFrustrumEventHandler();
+    public event ViewFrustrumEventHandler EnterView;
+    public event ViewFrustrumEventHandler LeaveView;
+
+    private bool visible = false;
+
+	void Update () {
+        Bounds bounds;
+        var renderer = GetComponentInChildren<Renderer>();
+        if (renderer) {
+            bounds = renderer.bounds;
+        } else {
+            return;
+        }
+
+	    if (visible && !IsVisibleFrom(bounds, Camera)) {
+            if (LeaveView != null) {
+                LeaveView();
+            }
+            visible = false;
+        } else if (!visible && IsVisibleFrom(bounds, Camera)) {
+            if (EnterView != null) {
+                EnterView();
+            }
+            visible = true;
+        }
+    }
+
+    static bool IsVisibleFrom(Bounds bounds, Camera camera) {
+        Plane[] planes = GeometryUtility.CalculateFrustumPlanes(camera);
+        return GeometryUtility.TestPlanesAABB(planes, bounds);
+    }
+}