Do you mean a 1st generation iPhone running the 2.0 firmware? If so, Pwnage does this already - it was released last week. I've unlocked and jailbroken my 1st generation iPhone running 2.0 with it and it works.
DAMN! how come when ever I put my iPhone on DFU or Recovery mode before Im gonna winpwn it, it never sees it? it keeps searching for the iPhone and iTunes opens up saying it had found an iPhone in recovery more and have to restore it.