The iOS 5 boasts over 200 features; however, Apple's video calling feature over 3G FaceTime is one of the features that did not make it to latest mobile operating system. However, there is a way on how to install FaceTime even if you are running in iOS 5.
FaceTime is a video calling application developed by Apple. FaceTime is for mobile devices running in iOS. FaceTime is supported on any iOS device with a forward-facing camera. Thus, it only works in devices beyond iPhone 4.
However, it is now possible to install the FaceTime feature in iPhone 4 by hacking one of the system files. Below is step-by-step procedure to enable the aforementioned feature:
Ensure that you back-up your devices first and store the files, photos and videos so you can restore the device if any error or issues arise.
Step 1: Download iFile for iPhone from Cydia or iExplorer for Mac and Windows.
Step 2: Browse to /System/Library/CoreServices/SpringBoard.app/.
Step 3: Open the file named N90AP.plist.
Step 4: Below the line, under capabilities, add in 3Gvenice.
Step 5: Save the changes you made and try the video calling feature.
FaceTime works by connecting an iPhone 4 or newer iPhone, a fourth generation iPod touch, a second generation iPad, or a computer with Mac OS X to another similar device; the previous generations of iPhone, iPod Touch, and iPad are not currently supported. FaceTime is not compatible with non-Apple devices or any other video calling services. The early 2011 revision of the MacBook Pro introduced high-definition FaceTime which may only be used with devices that have a HD FaceTime camera.
On the iPhone, FaceTime works in the Phone application instead of being a separate application. It can be activated when in the Phone application by placing a call, and pressing the FaceTime button. The FaceTime button replaced the Hold button (which is now available by pressing and holding the Mute button). The icon resembles a camcorder. It is also possible to initiate a FaceTime call directly from a contact file.
While the current FaceTime implementation for the iPhone does not officially support FaceTime calls over 3G (UMTS/HSPA), there are 3rd party applications that enable this capability for jailbroken devices. There are apps available in Cydia Store that allows you to use video calling feature of FaceTime in 3G. Jailbreak apps such as My3G let your jailbroken iOS device to have FaceTime.
FaceTime over 3G can only be achieved by using third party jailbreaking commercial software such as the FaceBreak, 3G Unrestrictor or My3G which fools the phone into believing that it is connected via Wi-Fi. These programs are only available on jailbroken iPhones via the Cydia Store. At the moment there are no free of charge solutions to unrestricted FaceTime. FaceTime uses about three megabytes of data per minute of conversation, so users with a limited data plan who use FaceTime over 3G (only on jailbroken devices as of right now) must be careful to not overextend their data limit. However, cellular talk time/minutes aren't used after switching from a voice call to a FaceTime call.
FaceTime on first generation iPad is also possible by porting the FaceTime application for the iPod touch 4th gen to iPad.