Daily comparison portscans

I would like to scan a number of hosts (~70) daily and compare the results
to a "baseline" scan that contains the accepted open port configuration.
This way I would know if any other ports open up that I didn't allow. I have
googled for this and found one post to the nmap hackers list that did
basically what I need but I'm looking for alternatives. Is anyone doing this
or does anyone have suggestions on how to do it?

Regards,
Ben