Yo

Yo is a very peculiar messaging app that, unlike similar tools, lets you communicate with other users using just one word: Yo.

So, what’s a Yo and why should you only want to say that to someone you know? Well, apart from being the first person singular pronoun in Spanish, yo is a word which you can use to simply transmit to someone that you're thinking about them. It means, in short, basically the same thing that giving someone a missed call meant earlier in this century.

Registering on Yo is very simple and doesn't require your phone number, email, or any other personal data. None of that. Just enter your name and password and you can start using the app straightaway.

Yo is certainly the most useless instant messaging app you can find on Android. And who knows, perhaps therein lies its charm.