You may not heard of Emoji icons (me too!) until the release of iPhone firmware 2.2. Emoji icons are actually picture characters that are very popular in Japan for text messaging. Nearly all mobile phones in Japan have Emoji icons built-in.
iPhone firmware 2.2 also comes with Emoji icons. But it’s only rolled out to iPhone users using Softbank network in Japan. Emoji icons are hidden from other iPhone users outside of Japan. Developer from Ireland, however, has found a way to enable this hidden feature. Now any iPhone 2.2 user can enjoy Emoji icon. The trick is to enable a property value on iPhone to bring out this feature:
You need to edit the file /User/Library/Preferences/com.apple.Preferences.plist on the device -> whether you use a jailbreak to achieve this or merely some iTunes backup editor is up to you.
Add the following boolean key as ‘true':
Enabling Emoji Icon using Cydia
For jailbreak iPhone user with Cydia installed, you do not need to edit this value manually. Cydia does all the stuffs for you. What you have to do is to open up Cydia and install Emoji under Tweaks section.
After installation, go to “Settings” -> “General” -> “International” -> “Keyboards” -> “Japanese”. Then switch on Emoji to enable Emoji icons.
Emoji icons can be used in most iPhone applications (such as SMS, email, notes, etc).
Note: If your recipient does not have Emoji icon enabled iPhone, the SMS or email with Emoji icons may not be displayed properly. You can refer to this Apple support article for details.