Add controls to show limits on a bar chart.  The bar will change colors based on whether its above or below the limit(s).  For instance, say I have a target of 50 widgets per hour.  The high limit will be 50.  The low limit will be 50*80%.  The bar will be red below the low limit, yellow above the low and below the high, green above the high.  Include the ability to attach a tag to the limit and perform a value transform on the limits.