So this popped up on Reddit:

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.