While not an option for Wildfire, apparently in Creo this has been improved:
from usecreo dot com/ten-new-capabilities-of-creo-parametric.html
8)Selecting Sketcher Reference “On The Fly”
Have you ever started sketching a profile and then realized you would like to snap the sketch to some underlying geometry? You can now add these references “on the fly” by holding the [CTRL] and [ALT] keys and selecting the edge, plane, vertex, etc.