You can get each data point's X-value from the "dataPoints" array on your series' "dataSeries" object. Using the SChartData protocol you can access each data point's X-Value using the "sChartXValue" property.
To get a line on today's date you can use our annotations feature. To see an example of this feature we have a AddingAnnotations sample which can be found inside the Samples folder of your Shinobi download.
More information on our annotations feature can be found here.