How to truly automate wordpress/plugin/theme updates

I have several websites that I use wordpress on, either as a standard blog, or as a sort of CMS. For various reasons, it isn’t possible for me to use the Multisite features of wordpress, so these are all separate installations.

Now, to the issue: WP has this nice “auto-update” feature, right? Yet, it isn’t really automated at all, you have to manually start it up and run it, give it a password if the site isn’t writeable by the web server, etc.

What I want is a *truly* automated way of updating my wp website, i.e, requiring *no* intervention from me. I want to be able to, for example, set a cron job that checks to see if there are any updates every night and go ahead and install them. For this I would need some sort of feed from wordpress about various things including new wp versions, new plug-in versions, new theme versions. Then I can write the script to do the update on the fly.

In some cases, I have plug-ins that when new versions are installed, I have to reset permissions as they overwrite the existing permissions and reset them back to the defaults which don’t allow the server to write into necessary directories. So I’d need to have sort of post-install initialization to ensure that such things are cleaned up.

At any rate, if someone has already done such a thing, I’d appreciate hearing about it.