As an addendum to my last post, I decided to figure out how to enable Emoji systemwide. My findings were first posted on Twitter, but I’m putting them here for persistence.

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’:

KeyboardEmojiEverywhere

Then merely go to the Keyboards section of the Settings app, hit Japanese, and turn on Emoji. Will work for any text field/view in the OS, including on websites, AND including the titles of items on SpringBoard (e.g. if you save a bookmark to the home screen). Have fun!