I have indeed written a channel hook (in Python) that saves any feed to a MySQL database. It's been working for a few weeks, and in the meantime I've been looking at what to do with the accumulating data.
One of the useful features of MySQL is its support in recent versions of FULLTEXT indices. I save feeds with FULLTEXT indexing so you can search them using various criteria.
I finally decided I needed a GUI-enabled program to permit easy searching. I first tried just creating an Awasu channel plug-in to do it, but found it too slow and awkward.
As often happens, on the way to formalizing the whole combination, I started thinking of alternatives. My current "detour" involves monitoring Awasu's progress as it updates channels and saving *all* successful channel updates to the database. This avoids having to specify which channels need the channel hook, but of course means updates for all channels -- whether really interesting or not -- get saved.
Now that this has turned into a public discussion, what of the things I have described would be useful, worthless, etc.? Any other ideas?