As announced yesterday, Dev Team member MuscleNerd did a demo of UltraSn0w, the new software unlock for the iPhone 3G (skip to 2.20 min on the video below). Unlike its predecessor YellowSn0w, UltraSn0w will unlock your iPhone 3G no matter what firmware, bootloader or baseband you have, as long as you have the new 3.0 firmware installed.
The actual program that UltraSn0w injects into the baseband to accomplish the unlock is the exact same one the Dev Team developed for YellowSn0w. What changed is that the Dev Team found a new “hole” to inject the unlocking payload.
During his demo, MuscleNerd successfully jailbroke his iPhone 3G and proved it by inserting a T-Mobile SIM card.
UltraSn0w won’t be available until Friday and like YellowSn0w, it will be downloadable through Cydia. Your iPhone will obviously have to be jailbroken and the Dev Team will release the necessary tools for that (QuickPwn and PwnageTool) soon.
Again, just to make this clear, there is no baseband downgrade needed. You can just upgrade to 3.0 tomorrow and wait for the Dev Team to push its unlocking tools and UltraSn0w on Friday.
Note that this unlock is only valid for the iPhone 3G. According to the Dev Team, this hack may be applicable to the new iPhone 3G S if it can be jailbroken, which should happen sometimes soon. Go Dev Team!