Using the SChartDelegate method crosshairMovedTo... is not the correct place to be implementing this feature.
As your current implementation would require a call to ShinobiChart's redrawChart method, which would create an infinite loop.
I would recommend adding your own gesture recogniser to your chart that uses the SChartAxis's dataValueForPixelValue: method to translate pixel values given when the user pans into data values.
Then you can update your data points and reload and redraw your chart. You could also show or move your crosshair using the SChartCrosshair protocol methods to keep your crosshair updated.