In absence of PwnageTool to jailbreak iPhone OS 3.1.2, GeoHot released an All-in-one jailbreak iPhone solution with the name BlackRa1n.
 

Now it’s dependable Dev-Team’s turn. MuscleNerd, a member of the Dev-Team, has announced the release of the new version of PwnageTool is almost imminent. The upcoming PwnageTool will be able to create custom firmwares to jailbreak iPhone 3GS, 3G, 2G, iTouch   and iPod Touch 2G.

PwnageTool let you create custom firmware for iPhone that only update the firmware version not the Baseband of your device so that you may use UltraSn0w then to unlock iPhone (3G and 3GS).