Lots of people love their iPhones but find there are some things about the handsets that don’t quite meet their needs. What’s their answer? They jailbreak their iOS devices to squeeze a little more out them.

Jailbreaking, despite its dramatic name, is completely legal — though it could void your warranty on your mobile device. Sometimes Apple’s designs frustrate users. For example, when Apple didn’t offer any multitasking on the iPhone, sa jailbreak community began providing that feature.

Sometimes a carrier hampers a device. AT&T recently cracked down on users of MiWi who used the app to tether their iPhones to their laptops, now that the network offers the service itself.

Finding jailbreak apps is easy. Cydia and ModMyi both act as a sort of app store. But before you run off and download anything, you should know: (1) Jailbreak apps are particularly vulnerable to becoming obsolete with every updated version of iOS, and (2) they do not go through Apple’s approval process, and there is a heightened chance of security risks.

Feel sufficiently warned? Here are some of the most popular and buzzed about Apple jailbreak apps:

LockInfo: Lock Info lets iPhone users customize their lock screen. It can show users when they have mail, text messages, calendar events, phone calls, voice mails and push notifications on the lock screen. It also displays the weather, Twitter feeds and RSS feeds. $7.99, which includes a 14-day trial.

BiteSMS: This texting app offers more features than the standard iPhone. Users can text from within other apps as well as from the lock screen. Other features included scheduled text messages and privacy settings that keep others from seeing whom you’re texting at a glance. You can use Bite SMS using credits (starting at $4.80 for 50 credits) or purchase the whole thing for $8.99.

WifiSync: As you may have guessed from its name, WiFi Sync lets you sync your iOS device over Wi-fi. Install the program on your Mac or PC and your phone to ditch the USB and sync music, apps, photos, contacts, calendars and e-mail accounts over wireless. Just remember: If you want to restore or update your device or iTunes, you have to uninstall the program and reinstall it later. $9.99

Xpandr: Similar to the Mac’s Text Expander app, Xpandr lets you make text shortcuts for commonly typed phrases on the iPhone. It can also help poor typists get around unfortunate mistakes due to AutoCorrect or fat fingers. It only works with firmware versions 3.0 and higher. $1.99

My3G: This little app lets you use Facetime over a 3G network — something Apple doesn’t currently allow. The app basically tricks the phone into thinking it’s operating on a Wi-fi network, which means it also works to run HiDef YouTube videos and VoIP apps on a 3G network. Just watch your data limits. $3.99

Tawkon: Tawkon measures the radiation leaking out of a handset and alerts you when radiation has increased over a certain level. The app made news last week when it was personally rejected by Steve Jobs (or, at least, someone with his e-mail address) with a curt, “No interest.” The app maps out places with low, medium or high mobile phone radiation and, when off a call, predicts what radiation levels would be if you made a call.

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Once the hobby of tech geeks, iPhone jailbreaking now a lucrative industry