Variable stroke width

This iPad version looks pretty fantastic for an initial release! I know features get added in, but there is one I really need to do the illustrations I need to do... Can you vary the stroke along a path, so it is thick on one side and thin on the other? There is the "Blob Brush" which makes a similar effect, but it creates an outline of the "path", not an actual editable line. Am I just not finding it, or is this not possible yet?

Thanks!

John