Pivotal Tracker does something like this with release markers. You can set markers between any two stories and, optionally, set a date. Tracker does a very simp

Pivotal Tracker does something like this with release markers. You can set markers between any two stories and, optionally, set a date. Tracker does a very simple moving average projection and if the stories before the marker will take too long, it turns bright red. I found it remarkably effective at getting business folks to actually prioritize. They don't believe you, but they'll believe the computer.