iPhone "jailbreaking" has been a hot topic since Apple released its smartphone more than two years ago. While the amazing little device does indeed have applications for "just about everything," Apple's sometimes arbitrary or self-serving rejections of apps such as Google Voice has turned more people on to the idea of freeing themselves from dependence on Apple for these resources (and also, in some cases, from AT&T for a network signal).
A collective of hackers known as the iPhone Dev-Team publishes easy-to-use, cross-platform tools that allow you to install third-party apps on your iPhone that Apple won't admit into its App Store.
For the moment, however, the legality of jailbreaking is in question. The Dev-Team offers its free tools without any proprietary code so as not to violate copyright laws. But Apple recently filed a statement arguing that jailbreaking constitutes copyright infringement because it incorporates a modified version of Apple's bootloader, the software that loads the main operating system.
Some jailbreakers are mostly interested in using their iPhones on a network other than AT&T's. Using a different network with your iPhone may get you better coverage, save some money on your data plan, or help when you're traveling overseas, but don't expect any tech support from Apple or AT&T. Unlike jailbreaking limited to loading third-party apps, jumping to a different network is not completely reversible, because of the changes it makes to the phone's baseband (modem firmware). The legality of this kind of jailbreak is even more questionable.
Suppose you're interested in a relatively simple jailbreak to experience third-party apps. This has some definite advantages, but some cautions to consider as well.
Pro: Rebellion Against 'The Man'
Apple argues that by keeping firm control over the hardware that runs its software, it's able to maintain quality and a consistent experience. But with all the App Store rejections, limitations on software developers, and usage restrictions (MMS is here finally, but where is tethering?), some people feel constrained by what the iPhone can't do. Apple has been very clear that it isn't happy with iPhone hacking, so if you're the kind of person who likes to rush out of the electronics store without letting the security guard check your receipt, you may find a rebellious thrill in jailbreaking.
Pro: Third-Party Apps Galore
Cydia and its newer, lighter competitor Icy are the unofficial app stores available only to jailbreakers. In these stores, you'll find hundreds of terrific apps that have been rejected from the App Store for providing features that Apple would rather you not have. Examples? Cycorder is a camera app that enables video-recording on pre-3GS iPhones; PDANet allows tethering of your 3G connection to your laptop; and GVMobile is an app for the Google Voice service. Plus, you can still get free and paid apps from the official App Store, so jailbreakers get the best of both worlds.
Pro: Total UI Customization
The iPhone's user interface is excellent, but there is just something cool in giving your phone a Snow Leopard facelift. Or making your home screen look like a vending machine. Jailbreaking lets you do that, and much more. With the Winterboard app, you can install any of the vast number of skins available. Jailbreaking also lets you install systemwide add-ons such as SBSettings, which enables quick access to your system settings from within any app. You can even add a fifth icon to the dock at the bottom of all iPhone screens or change system sounds (like adding some new text message tones to the scant built-in set of six). The list goes on and on.