Notifying assignee of linked issue when linked issue is resolved

In the way we've structured JIRA issues we have 'block' links mapping the progression of a project.

For instance:
Planning issue blocks Development issue
Development issue blocks QA issue
QA issue blocks Launch issue

The feature i'm looking for is someway for the assignee of the blocked issue to be notified when the blocking issue is resolved (or closed), so they know they can start work.

Currently I know of no way for the assignee of the blocked issue to get a notification when the blocking issue is resolved (or closed). The only way I know to do this is for the person to watch the issue, but that creates too much information flow, the assignee of the blocked issue just needs to know when they can start working (blocking issue is resolved or closed).

I'm not sure the best way to do this, so I'm open to your suggestions.
If anyone has found workarounds or there are plugins out there, please post those too.

Thanks,