// response comes from the OnlineMapsOSMAPIQuery
private OnComplete(string response)
{
        // Some stuff which gets a node from OSM

        OnlineMapsMarker3D marker3D;
        OnlineMapsControlBase3D control = GetComponent<OnlineMapsControlBase3D> ();
        marker3D = control.AddMarker3D (new Vector2 (node.lon, node.lat), markerPrefab);
        marker3D.label = node.id;
        marker3D.OnClick += OnMarkerClick;

        Debug.Log ("DEBUG: " + String.Format ("Long: {0}, Lat: {1}", node.lon, node.lat));

        markers.Add (marker3D);
    }
}

private void OnMarkerClick (OnlineMapsMarkerBase marker)
{
    Debug.Log ("DEBUG: " + marker.label);
}