Frustum Checking

public static class GameObjectExtensions {
	public static bool IsVisibleFrom(this GameObject obj, Camera camera) {
		Bounds b = obj.GetComponent<Collider>().bounds;
		b.Expand(0.5f);
		Plane[] planes = GeometryUtility.CalculateFrustumPlanes(camera);
		return GeometryUtility.TestPlanesAABB(planes, b);
	}

	public static bool IsVisibleFrom(this GameObject obj, Plane[] planes) {
		Bounds b = obj.GetComponent<Collider>().bounds;
		b.Expand(0.5f);
		return GeometryUtility.TestPlanesAABB(planes, b);
	}
}

/** Math utility. Put inside a static helper class somewhere**/
		public static Plane[] CalculateFrustum(Vector3 origin, Vector3 direction, float fovRadians, float viewRatio, float distance) {
			Vector3 nearCenter = origin + direction * 0.3f;
			Vector3 farCenter  = origin + direction * distance;
			Vector3 camRight   = Vector3.Cross(direction,Vector3.up) * -1;
			Vector3 camUp      = Vector3.Cross(direction,camRight);

			float nearHeight = 2 * Mathf.Tan(fovRadians / 2) * 0.3f;
			float farHeight  = 2 * Mathf.Tan(fovRadians / 2) * distance;
			float nearWidth  = nearHeight * viewRatio;
			float farWidth   = farHeight * viewRatio;

			Vector3 farTopLeft  = farCenter + camUp*(farHeight*0.5f) - camRight*(farWidth*0.5f);//new Vector3(-camRight.x * (farWidth*0.5f), (farHeight*0.5f), -camRight.z * (farWidth*0.5f));
			//Vector3 farTopRight = farCenter + camUp*(farHeight*0.5f) + camRight*(farWidth*0.5f);//new Vector3( camRight.x * (farWidth*0.5f), (farHeight*0.5f),  camRight.z * (farWidth*0.5f));
			Vector3 farBottomLeft  = farCenter - camUp*(farHeight*0.5f) - camRight*(farWidth*0.5f);//new Vector3(-camRight.x * (farWidth*0.5f), -(farHeight*0.5f), -camRight.z * (farWidth*0.5f));
			Vector3 farBottomRight = farCenter - camUp*(farHeight*0.5f) + camRight*(farWidth*0.5f);//new Vector3( camRight.x * (farWidth*0.5f), -(farHeight*0.5f),  camRight.z * (farWidth*0.5f));

			Vector3 nearTopLeft  = nearCenter + camUp*(nearHeight*0.5f) - camRight*(nearWidth*0.5f);//new Vector3(-camRight.x * (nearWidth*0.5f), farCenter.y + (nearHeight*0.5f), -camRight.z * (nearWidth*0.5f));
			Vector3 nearTopRight = nearCenter + camUp*(nearHeight*0.5f) + camRight*(nearWidth*0.5f);//new Vector3( camRight.x * (nearWidth*0.5f), farCenter.y + (nearHeight*0.5f),  camRight.z * (nearWidth*0.5f));
			//Vector3 nearBottomLeft  = nearCenter - camUp*(nearHeight*0.5f) - camRight*(nearWidth*0.5f);//new Vector3(-camRight.x * (nearWidth*0.5f), farCenter.y - (nearHeight*0.5f), -camRight.z * (nearWidth*0.5f));
			Vector3 nearBottomRight = nearCenter - camUp*(nearHeight*0.5f) + camRight*(nearWidth*0.5f);//new Vector3( camRight.x * (nearWidth*0.5f), farCenter.y - (nearHeight*0.5f),  camRight.z * (nearWidth*0.5f));
			Plane[] planes = {
				new Plane(nearTopLeft,farTopLeft,farBottomLeft),
				new Plane(nearTopRight,nearBottomRight,farBottomRight),

				new Plane(farBottomLeft,farBottomRight,nearBottomRight),
				new Plane(farTopLeft,nearTopLeft,nearTopRight),

				new Plane(nearBottomRight,nearTopRight,nearTopLeft),
				new Plane(farBottomRight,farBottomLeft,farTopLeft)};

			return planes;
		}