I'm not sure how common the need for this is, but I have the need to call out pocket depths on plan views of drawings for simple router cut parts.
Currently I can use a leader and pull in a Parameter value of an extrusion feature, so that the depth is intelligent and will update if the extrusion depth changes. But if a move face or thicken feature is added, the extrusion dimension does not reflect the pocket depth accurately. I'd like to be able to specifiy a face or plane as the top of material and then select pocket faces to place the pocket depth callouts.
A simple example of a part with routed pockets and the call outs I'd like to have:

Related Link:
http://forums.autodesk.com/t5/Autodesk-Inventor/Extrusion-Depth-Callout-in-IDW/m-p/1341235