Yo: That's all this app can do

While there are many fairly specialised mobile apps out there, Yo, which was just launched by Life Before Us, takes the cake for being the narrowest-focused messaging service available on Android and iOS now.

Why? Because Yo can only be used to say "Yo" to your contacts. As you can imagine, it does not even trigger a keyboard when you want to hit a friend with a message, as a touch of a button will do the trick (Life Before Us touts this as a feature, in case you are wondering why the heck I am mentioning it).

I'll leave you with the description:

The simplest & most efficient communication tool in the world.

So, Yo! (Oh, and a bunch of investors raised $1 million (over £586,000) to make Yo happen.)

Yo is available to download from Apple App Store (iOS) and Google Play (Android), but, really, would you want to use it?