@chartguy,
You can sync crosshair & toolTips across charts by getting the pixel co-ordinates from the first chart & then triggering an event in second chart and so on. You can use convertValueToPixel() and convertPixelToValue() methods to get the pixel co-ordinates & corresponding values. Here is a jsfiddle for the same. Please note that there may be a slight variation in x-value as pixel co-ordinates are used.
—
Vishwas R
Team CanvasJS