ZiPhone - Unlock, Jailbreak, Activate, REPAIR your iPhone - NO DOWNGRADING REQUIRED!
THE SIM UNLOCK PART OF THIS ONLY WORKS ON OTB 1.1.2 and 1.1.3 IPHONES!
Source Details available here
But as there is no instruction as yet here is a guide with downloads, tutorials and more info.
I like this bit:
As a side-effect, using this tool will revive many 'dead' basebands.Just use the unlock option.
FOR PEOPLE with NO IMEI, NO WIFI, NO BASEBAND (4.6BL):
So all those people with ibricks can now enjoy there iPhones again!
Check out this screenshot!
I haven't tried this and won't be so I'm unable to help with this (sorry) but apparently ts incredibly easy to use, and is available for both OS X and Windows