ok, how about this:
you create a bash script, run from cron every single day, and what it does is it downloads the latest tar.bz2, creates a pkgbuild (pretty much changing to the latest md5 and version number only) and install it on your system, then you manually try the package on your system.If everything works fine, then you upload it. you can make that your daily morning rutine or something and using scripts is not gonna be really time consuming or annoying.
--- El jue 27-oct-11, Maciej Sitarz
Sounds like it might be a candidate to recast as a -vcs package, if upstream makes the contents of the tarball available over some vcs system...
Only tar.bz2 is available on the project website. -- Maciej Sitarz