Unlock 3GS Firmware: 06.15.00, Version: 4.2.1 (8C148a)

Hi guys,

I have an iphone 3GS with
Formware: 06.15.00 and
Os Version: 4.2.1

It is currently tethered jailbroken and unlocked. As you already may know the problem with tethered unlock is I have to attach it to a computer every time i power start it.
It has been very annoying for me so far. I wonder if there is any way, I can unlock it untethered.

Any suggestion/help would be appreciated.

1) Please don't threadjack, your post was unrelated to the thread you posted in. I've split it out to its own thread.
2) The answer depends solely on whether or not you have a 4.3.3 SHSH or a 4.2.1 SHSH (you don't *need* the iOS 4.2.1 SHSH, but it would be handy to have to ensure you could restore right back to where you are right now before doing anything). There is an untethered jailbreak for iOS 4.2.1 on the 3GS (using redsn0w 0.9.6b4), but it's always worthwhile to have an SHSH on file when you attempt to re-jailbreak. You can use redsn0w 0.9.6 RC16 to jailbreak iOS 4.3.3, and iOS 4.3.3 also has an untethered jailbreak using Jailbreakme v3 -- but you'll need a 4.3.3 SHSH to successfully restore to iOS 4.3.3 at this point, as Apple is no longer signing it.

For SHSH information, click the SHSH link in my signature.

Good luck!