average website daily visitors

Hello all ,
I'm creating a website that will serve the WEBSITE OWNERS .. one of the services I want to include in my website .. is a form that the visitor will write his website URL or any Website URL in it , and hit the submit button to show him how many users visit this URL daily ..

Is there any hint or script to get or calculate the number of visitors that visit a domain name (not my domain .. But any domain) on a daily basis .

Example for what I want is found in www.statbrain.com
Please.. this topic is so important to me .. so any hint , any hint will be useful to me .
thanx in advance

You won't be able to do this for any website that someone plugs in.
Some code is needed on each site to do the tracking.
If you have a goooood friend at google you might manage. Even then doubtful as even google doesn't know about every site out there.

To be accurate it is going to require them to at least put some script on there site.