OS X V10.7 Lion :: Custom Metadata In Spotlight?

If you open Spotlight using Ctrl+F, you get an interface for advanced queries. Under "Kind", you can select "Other..." and Spotlight opens a list of "search attributes". It's a long list but of course not complete. Question: is there a way to add custom metadata attributes that can be read by Spotlight? I am willing to get my hands dirty with plists and such, or perhaps there is some freeware add-on that can facilitate this? 

1. I can create a new search attribute for OS X files -- let's call it "foo". 

2. I can attach the value "bar" to the metadata attribute "foo", e.g. for the file "myFile.txt". 

3. I can write an AppleScript that takes a file name as a parameter and returns the value of the "foo" attribute. I.e., I give it "myFile.txt" and I get "bar" as the result. 

4. I can use spotlight to search for "bar" and get all files with this metadata. 

5. (Optional) I can use spotlight to search for "foo:bar" and get "myFile.txt". 

I have looked at a bunch of things on the Net (OpenMeta, SpotMeta, etc.) but I haven't found anything yet that will do this. 

Info:
MacBook Pro, Mac OS X (10.7)