GroupMe (www.groupme.com) is a popular app from Microsoft that enables teams (or simply groups of friends) to collaborate and enjoy the transfer of photos, while making use of both data or SMS for messages. It's available on iOS, Android and even has a web version.
The team has pushed out second, rapid update for the app this week, introducing new emoji support (also available in the GroupMe apps on other platforms) as well as fixing some lingering issues.
The reason the GroupMe team decided on adding their own emoji was due to other apps offering emoji that don't feel as natural as entering text to compose a message. Instead of showing the actual emote in the message compose box, a ":)" or "[smile]" may be present until the message has actually been sent. With any GroupMe app, the emoji will be displayed correctly and shall be fired across the world to the recipient with style.
Utilising the same idea as a WYSIWYG (What You See Is What You Get) editor, you'll effectively be able to edit the message, knowing it'll be rendered exactly as is on the recipient device. Neat.
Version 188.8.131.52 was just released today bringing back text prediction as that feature was temporarily removed due to a conflict with the new emoji system. With this latest update, those who were experiencing crashes or missed the autocorrect feature, you should be on better grounds with this release.
You can download GroupMe from the Windows Phone Store (available for Windows Phone 7 and 8).