Hat tip to iJustine (and Brent for letting me know):

1. Buy http://go.tagjag.com/emoji in iTunes (.99c)
2. Install and click through any story in the app.
3. Go navigate through the iPhone’s Settings: General | International | Keyboards | Japanese | toggle Emoji to on
4. SMS emoji graphics to anyone else who uses an iPhone – just click the globe symbol that should now appear in the SMS keyboard!

There’s also a way to do this for free (but in my estimation, it’s easier to just spend .99c on the app that’ll do it for you automatically).