You could do this with a rule, but I got tried of doing that and wrote a custom app to do exactly what you want instead:
The Notifications app would likely not work well here, since it's designed to respond to events in real time (or with a delay if the condition the event caused to be true is still true), not really check on demand like this.
That being said, if you prefer a rule over custom code, I have an example of the rule I used to use in that post, too. 
So that should give you one idea of how you could do this in RM. Hope this helps!
