Hey tmbuk!
I actually just wrapped up building a workflow that does this for myself today and decided to search the forum to see if anyone did anything similar and I found this post! Glad to see someone else thought to do this.
I figured out how to get Alfred to show the text passed with {query} within Notification Center. Turns out that the Keyword input had to be directly attached to the Post Notification output, not the script itself.
Check it out here: http://db.tt/b4YauDLj
(New users, don't forget to enter your API Token and User Key in the script!)