Actually, I don't know... I worked on a project a few months ago where I needed to redirect pages based on mobile devices and I just googled around until I found those. I seem to remember finding more than half of them on a PDA application development site and the others just here and there.
I was also thinking that it may be better to use a browser resolution detection script instead of looking for matches in HTTP_USER_AGENT since you would have to continually update the string list based on new devices. I have seen JavaScript that would do that, but I’m not sure if all mobile devices can even run JavaScript.
Maybe a combination of both solutions would work. Redirect if there is a match in HTTP_USER_AGENT and if not, check the browser resolution with JS.
Just a thought.
-Z