I basically run an ecommerce website. I wanted to know if there is some tool which I could use to check if the IP a user registered with matches with the address he entered. I bet JodoHost must be using something because they emailed me when I first registered here saying that my IP and billing address didn’t match.. obviously I was on holiday 
Well for payments, our payment gateway tell us if the IP matches or not. For trial account activation (its no more automatic anymore), we use http://www.youngzsoft.net/ip2location/index.php to verify the IP location