There is no ability to add tools to ArcGIS.com. You'd have to write your own JavaScript, Flex, or Silverlight app. Look here for the help resources...http://resources.arcgis.com/en/home/FYI, we will be adding point to point directions in the ArcGIS.com Map Viewer in the upcoming release in March for organizations that have purchased a subscription to ArcGIS Online.Thanks,Mike