I've actually been working on something myself. It's fairly different in approach though. I've outlined some of my thoughts on it here

This has wound up to be a pretty big project for me with more to go in the not-too distant future, but thought you might be interested in another-WTDI.

as to debugging, I always _try_ my SQL out from the command line first, just to check out i haven't gotten things all befuddled. Additionally I always check for errors on every step of a sql call, and when one occurrs I dump the full sql query string out at the same time that I output the error message. It's VERY helpful