If you rely on a software based unlock for your iPhone 4 and are stuck on a higher baseband like 2.10.04 / 3.10.01 on iPhone 4, the only way to unlock iPhone 4 up till now was through the Gevey SIM interposer which can unlock iPhone 4 baseband 2.10.04 and 3.10.01 by forcing baseband activation via the emergency dialler. While Gevey SIM iPhone 4 unlock is illegal, there is another solution for unlocking iPhone 4 baseband 2.10.04 and 3.10.01. A hacker named Dill Huang has been able to unlock iPhone 4 on the above mentioned basebands, without requiring Gevey SIM. As proof, he has also posted a video.
First, he inserts the SIM with the real IMSI value and dials 112 and then hangs up after 2 seconds. He then toggles the iPhone into flight mode and removes the SIM card. Then he inserts the SIM with the test IMSI and toggles flight mode off and voila, the iPhone 4 is unlocked on baseband 3.10.01.
Once again, you won’t be able to do this unlock procedure on your own device, however lets keep waiting for the 40 bit NCK hack for unlocking iPhone 4, that the iPhone Dev Team is working on.