Checkurls is not part of the GNU Project.
Checkurls is a files changes checker.
It can help you reduce the time you lose checking for updates, letting you to read only the new things.
It monitors a list of files, and if a file changed it sends the changes to you by email, so you can use your preferred mail user agent to read them.
It has options to report only the added text, only the removed text, both, HTML to Plain-Text redering, minimum and maximum lines to report.
It is meant to be as much configurable as convenient.
UPDATE: checkurls is unmaintained. Please contact me to apply for maintaining it.
The documentation is included in the Checkurls package in info format, including texinfo sources too.
There is a specific mailing list where you can ask for help: <http://lists.nongnu.org/mailman/listinfo/checkurls> (public mailing list with public archives).