updated 06:00 pm EDT, Thu May 10, 2012
Tool could be available within weeks
[Updated: video added] Chronic Dev Team hacker Pod2G, who reported last week of being able to get an untethered jailbreak running on an iPhone 4, has updated his progress with further news. He has gotten the jailbreak exploit to work on most other iOS devices capable of running iOS 5.1, regardless of processor type. The breakthrough, which may not apply to the latest iOS 5.1.1 update, could mean a public tool for untethered jailbreaks will arrive soon.
The jailbreak technique is not yet available for public use, as Pod2g reports that it needs stabilizing and packaging, but the news gives hope to iPhone 4S and third-gen iPad users who had been looking for a jailbreak method in order to use some customizing and non-App Store apps. He reports that the third-generation Apple TV device hasn't been tested yet and may not work with the hack. He also plans on testing the exploit with iOS 5.1.1.
Jailbreaks rely on OS exploits in order to inject altered ROM code into the firmware of the device, but it generally needs to be customized for each different processor. An "untethered" jailbreak is ideal, as it is persistent across restarts. A "tethered" jailbreak, which is already available for some iOS 5.1 and 5.1.1 devices, must be re-applied by attaching the device to the computer after any restart or power-down. Other developers are also working on untethered jailbreaks for various iOS devices.
The process of getting the jailbreak into a publicly-usable form may take a while, but it looks increasingly likely that an untethered jailbreak should arrive before the next major release of iOS, giving many users the option of running a jailbroken device. Owners of older devices in particular often experiment with jailbreaking to help extend the useful life of the device, or gain abilities that no current App Store app offers.
Users under warranty are cautioned that Apple will not fix any problems it suspects may have been caused by the jailbreaking process. In most circumstances, the device can be reset to factory settings, but sometimes this is not possible (known as "bricking" the device).
Update: Pod2g has added a video demonstrating the untethered nature of the jailbreak (below). In it, he demonstrates an iPad that is running iOS 5.1 that remains jailbroken after a restart.