Question about ports adding cronjobs

[David Hawthorne]

I have a piece of software I've been working on that gathers stats  
about the local host and shoves them into rrd files, with an  
accompanying web front-end page that generates pretty graphs from the  
RRDs on demand.  I have a package done up for it, and I'd like to add  
it to the ports tree eventually, but I'm stuck on how to get it to  
automagically add the cronjob to have the stats gathering script run  
every five minutes, and I don't know of any ports that add cronjobs  
off the top of my head to go look at.

Is there an approved standard for doing this?  It doesn't have to be  
as root, either, it can run under a different user.  Any advice on how  
to get the port to add the user (and remove it properly when the port  
is deinstalled) properly and securely would be appreciated as well.

Bonus points for providing the lines that would need to go into a  
CONTENTS file for the package, because that's what I'm working with  
right now for testing it on multiple machines.

Thanks!