what can you do if the ipod touch is jailbroken?

I'd say not because the ipod wouldn't have a connection to any network. There is no cellular radio in the device, so the only way it can communicate is via wifi.

You can do it for any iPod touch, no need for jailbreak (I don't advice jailbreaking).

Buy an on the go 3G box. Follow this link:

http://blog.comcast.com/2011/05/get-wifi-everywhere-you-go-with-our-new-4g3g-mob ile-hotspot.html

Unauthorized modification of iOS has been a major source of instability, disruption of services, and other issues

read this: http://support.apple.com/kb/HT3743