I don't have mine cronned yet.. just run the php script every once in a while. Won't be instant updates but no big deal.
You could also do something like this at the top of global:
PHP Code:
if (mt_rand(1,500)=='42' or $updatesigstats!=''){
require_once('/home/yourdir/sigstats.php'); // the full script name of your sig updater
}
About once in every 500 page views, it will update the signature stats. Or you can attach "&updatesigstats=on" to any URL and have it run the script as well.