Using the date of last modified file? (not use the date in the info, which always remains at the discretion of the maintainer)
I suggested the appbrowser but could also be a mailing list for updates, or simply a dynamic table on the web.
Example to explain my point of view:
1-Manteiner creating 3 packages with 15 total dependecies.
2-One or more of these dependencies are updated.
3-A mailing list inform automaticly a members of changed (or a feed, or a order in appbrowser, or table in web page).