can ipod touch acess internet from anywhere or does it need a location with wi-fi?

I was wondering if the ipod touch can acess the internet from anywhere or does it need a location with a wi-fi signal? If so is there an app or acessory that would allow it to generate its own? For example, I go to flea markets and antique stores on a regular basis and sometimes want to price something. Usually there is not a store anywhere nearby to generate a wifi signal.