Need jailbreak iPhone. Start Cydia and setup app Emoji (from repository iSpazio). And go to Settings -> General -> Keyboard -> International Keyboards -> And Enable ‘Emoji.’

You can do this yourself.
Annex only adds key ‘KeyboardEmojiEverywhere’ with flag ‘true’ in file /User/Library/Preferences/com.apple.Preferences.plist.

Or setup “Touch Dial Emoji” from apple store.