Unlock iPhone 3GS, 3G Ultrasn0w 1.2 on iOS 4.2.1

The iPhone Dev Team has just released ultrasn0w 1.2 which brings carrier unlock for iPhone 3GS and iPhone 3G on iOS 4.2.1 or iOS 4.1.

How to: Jailbreak iPhone 3GS / 3G on iOS 4.2.1:
STEP 1: Unlocking requires that your iPhone is jailbroken. Download PwnageTool from link given above and use it in Unlock edition to update the baseband to 06.15.00. Also note that there's a version of Redsn0w will be out tonight for Windows users to update the baseaband.

How to: Unlock iPhone 3GS / 3G on iOS 4.2.1:
STEP 2: Once you jailbreak yoour device, you can now unlock your iPhone on baseband 06.15.00 using Ultrasn0w 1.2 from Cydia. To do so, follow the steps below:

• Press to launch Cydia Installer from your SpringBoard.
• Press to select the Manage tab at the bottom of the screen.
• Press to select the Sources button

• Now touch on Edit and then on Add. You will be prompted to enter the URL of the source. Type http://repo666.ultrasn0w.com and touch on Add Source to add this repository. 

• Once the source has been added press the large Return to Cydia button then select the Done button at the top right of the screen.
• Now select repo666.ultrasn0w.com from the sources list and at last select ultrasn0w from the list of packages as shown below then install this application.

STEP 3: Almost done, now simply reboot your iPhone and you should have a fully unlocked iPhone 3GS on iOS 4.1 or iOS 4.2.1.

Unfortunately, iPhone 4 unlockers have to wait a bit longer before they can use their device on any carrier they like but at least they had promised to start working on that starting from tomorrow.