I wonder why are you so concerned about this. If you are root you should be the one creating the accounts so you shouldn't need any notice.
Still, you can use inotifywait, from inotify-tools (assuming that your kernel is recent enough to support inotify).
inotify-tools
With that tool you can monitor many events on a given point of your filesystem (i.e. /home) like creation of files/dirs for example. Of course, this will only work if you system is configured to create the home dir at the same time that the account is created.
If not, you could still use inotifywait to monitor /etc/passwd for modification.