Geo Hot’s PurpleSn0w Unlock
Geo Hot has released purplesn0w which is an iphone 3G S carrier unlock. This Purplesn0w unlock is suppose to help people having wifi, signal, and battery issues using the Dev-Teams Ultrasn0w unlock. It seems to me we have a little team battle here.. I like to see competition as this will drive the teams to better them selves and release more stable software solutions for the iphone community. Here is an excerpt from Geo Hot’s blog about his software based unlock solution:
“purplesn0w technicals
About a year ago today, I found the at+stkprof exploit. Back then, I struggled for 3 days to write a payload. No luck, I just wasn’t a good enough reverser. So I stashed the exploit away until December, when I gave it to dev for use in yellowsn0w.
Now a year later, I wrote a payload and delivery system in a day. And it’s an awesome payload. Ideally we’d like to patch the lock out of flash, but with the apparently proper sig checks, that isn’t going to happen. So purplesn0w is the next best thing. I copy the page I want to patch to an unused region of memory. In memory I patch it. Then, using the MMU, I map the flash page out and remap the patched memory page in it’s place.
No new iPhones are really unlocked, activation creates a ticket allowing the baseband to be used with that sim. The lockstate of the phone really lies on apples servers. Unlocked is auth all sims. Locked is auth AT&T sims only. Fortunately this ticket system provides an easy way to deliver the payload and reexecute the patched code all in one. And since the ticket is already delivered on baseband resets, theres no need to write another daemon to hog battery. I use the daemon already designed for this, lockdownd. A patch to commcenter gets it to run the payload on ticket delivery. And a patch to your activation record contains the payload. So using existing apple machinery, I unlock when needed.
In retrospect, I should’ve just patched commcenter to send the payload. Then hacktivation would work no problem. Oh well, tomorrow is another day. I’ll add hacktivation support then.
Here is the source. And I mean all of it.”
Note: As you can see in the post below, do not comment sayng that it doesn’t work. You need to meet those certain requirements, the main one being that you have to activate your iphone through itunes using a legit AT&T sim card for purplesn0w to work. Hacktivation support will come within the week 
Warning: PurpleSn0w is still in beta and some people report that the unlock solution has made them go into the spinning wheel of death and they had to restore iphone.