Last week a video made the rounds showcasing a new way to bypass Apple's many layers of security on the iPhone. The software called PwnageTool, which has been released today for both Mac and Windows users, opens up the iPhone to running apps that have unsigned code, effectively letting users run homebrewed developer apps with no special seals of approval or verification whatsoever. The tool also lets you load up your phone with customized firmware, letting advanced users develop their own concoctions that could be shared with other users, complete with automatic unlocking, jailbreaking, and activation upon first boot.
You can watch a video of the tool in action below. There are also download links, as well as documentation here. Keep in mind using this third-party software in its early stages is a very easy way to brick your iPhone if you don't know what you're doing. You're also voiding any warranty you have through Apple, so if you're eager to give it a spin, my advice is to wait a few days for them to work out the kinks.