Definitely read up on Strongbox, the Ikonworks recommened,
before using any of the naive "count the IPs" scripts.
Strongbox is like a bank vault compared to password sentry's piggy bank.
It is truly the next generation protection.
You can find some info here:
http://www.bettercgi.com/strongbox/
or here:
http://www.webmastersguide.com/?htaccess-cgi/strongbox/