EmoYo is an app clearly inspired by the simplistic nature of Yo. both in name and design. Quite interestingly though, the creator is only 16 years old. The app's sole reason for existence is to add friends and share your emotions with each other easily and without any other context. It's free for the iPhone and requires iOS 7.1 or later.
As with Yo, there's not very much happening in EmoYo. When you sign up, you're asked to enter your email address, plus pick a username and password. Tapping inside the password box for some reason brought up the numeric keypad rather than a full QWERTY keyboard, forcing me to restrict my password to only digits. For security purposes, the developer should address this in a future update.
Congratulations, you have now signed up for EmoYo. How are you feeling? If you tap "Emotion" on the top right, you have nine different answers to that question: happy, sad, mad, excited, busy, confused, relaxed, sick or in-love. Each one carries its own color.
The design of EmoYo is nice and fits in quite well with iOS 7's new design principles. However the overly thin font choice (I'm guessing some extremely light variation of Helvetica Neue) sacrifices legibility in favor of aesthetics, which is a no-no. The emotions are particularly hard to read on darker colors, and this applies throughout the app. In the early betas of iOS 7 in 2013, Apple used a light font as the system-wide default before switching to a slightly thicker Helvetica Neue for the same reason this app should.
Once you choose how you're feeling, your friends in the app will see your username over that emotion's color as well as the emotion itself. If you have multiple friends they all just appear in a multi-colored list. At the bottom of that list is a Plus button to type in someone's username and add them as a friend.
That's the entire app. It's a bit buggy at the moment too, but that's nothing an update can't fix. To say EmoYo is minimalistic would be an understatement. I wouldn't go as far as to say the app is crude, but it certainly has more potential. Down the road, I could see an EmoYo with built-in functionality to react to your friends' moods. For instance, if a friend is feeling sad, with one tap send a text message wishing them well. Perhaps even integration with a third-party service to send a small gift isn't out of the question.
For now, the biggest challenge EmoYo faces is but one question, yet it's a question anyone who finds the app will inevitably ask: "Why do I need this?" If your friends are feeling a certain way, chances are they're already tweeting about it or texting you about it. A separate app dedicated to merely sharing emotions just isn't necessary. If this concept happens to intrigue you, EmoYo does a fine job with it so by all means, indulge. Otherwise, EmoYo feels a bit too bare bones to appeal to the masses.