Make sure you know how to do jailbreak because there are a lot of those things on net and more than %70 damage your iphone.
Jailbreak is the hacked software that able to used all the crack version of applications. I had try both on iphone and ipod the benefit of doing that is to help you getting all paid applications for free but the risk is giving your iphone and ipod stuck or slow sometime and most of the thing it's annoying with the whiteboard need to be update all the time when you're connect to internet.