I use Text to speech for adding different voices in my tutorial videos, also speech to text to write long and boring content jobs and sometimes I am too tired or lazy to rub my fingers on keyboard. But recently I came across an app called SpeakEmoji which convert whatever you say it to an emoji. Basically you speak any emoji sign, so this app can understand and choose related emoji. You can download and install this app from Android play store and it's also available for iOS.
Check out their Intro Video :-
You can also enable this app on your typing screen and use it which using keyboard from the app. You will need go through a small setup and then you can use it from any screen or within any application. It could be more useful if it can translate emojis to text too but for now it works in one direction only, using this app on whatsapp is very cool.