Extensible Dependencies ’N’ Actions (EDNA) for Org Mode tasks
Edna provides an extensible means of specifying conditions which must be fulfilled before a task can be completed and actions to take once it is.
Org Edna runs when either the BLOCKER or TRIGGER properties are set on a heading, and when it is changing from a TODO state to a DONE state.
For brevity, we use TODO state to indicate any state in org-not-done-keywords, and DONE state to indicate any state in org-done-keywords.
(from nongnu.org: http://www.nongnu.org/org-edna-el/)
I don’t have time to dig into this right now but this looks particularly interesting.