I wrote a small script a while ago to automate the pkgsrc/kernel(src) anoncvs updating process, you can go ahead and check it out: naupd
It's written in python, and requires CVS.. I am working on importing the pyCVS module or writing a small class to handle the CVS protocol, and cleaning it up a bit .. but for now, the current beta is very much functional and I use it to update pkgsrc daily (/usr/local/bin/naupd -p).
hope its useful.
Re:
I wrote it for those moments where you ponder to yourself.. "okay.. it's 5am, I randomly woke up to burn some random iso and my system lacks the cdrecord pkg and crond updated my cvs sources yesterday.. and it has not updated yet and uh I'm too lazy to execute the anoncvs (environment/cvs) calls and oh no pkgsrc.netbsd.se shows a new release too.. ehh.. mhmm.. food...".
etc.