In my article, Two Secret Features of Quicksilver, I've discussed how to use Quicksilver to set a delay before running application.
Roughly, I believe you've already known how to create automator application to speak text which have been discussed here. In case you don't want to waste your time creating the application, I've created an application to only speak up "Time's up!" when it's launched; It can be downloaded here.
Let's say you want your automator application to alarm you two hours two minutes and two seconds later, then these are what you need to do :
Run After Delayand Set the additional info to
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