Higher authorities could easily find out about criminal activity - such as drug trafficking and child pornography - being conducted on a laptop simply by hacking into it or somehow seeing the history.
No, they find it out from the web history/logs, which is with the internet service provider (verizon, comcast, etc). They don't need access to the computer for this.
Basically, when you access the Internet, your data is routed between various servers. Some belong to your ISP, some belong to your "ISP's ISP" (the servers which give the ISP their internet), and some belong to the ISP of the destination site, as well as a few more hops in between.
When you use an https connection, the _data _ is hidden, but the URLs are not. With an HTTP connection, an eavesdropper can read everything.
Either way, most ISPs log URLs and snippets of data, and the police can request access to these logs. Then they know who visited what.
If you use an anonymizing service like Tor, the police shall find it much harder to track you. Not impossible (a lot depends on how you use it -- you need to be very careful if you don't want to be tracked), but very hard.
However, the iPod Touch - or any tablet device that can access the internet that isn't a phone - is next to impossible to hack.
Where did you see that? If this was the case, then jailbreaks would never be released.