3G / Wifi Checker

Hi everyone,
I was just wondering if there's a script (or something similar) to check if a user is connected to my site using the Wifi or the 3g.
It would be super usefull. You could handle differents ADS behaviours knowing the user connection.
Thank you all

I doubt your browser or user system would pass through connection data, other than IP address and unless the service provider has specially make public which IP's they use for 3g or hardwired, I doubt you'll receive that information.