A free app for Android, by TheBurraq.

Write SMS By Listening: Voice Text Message Sender is the best app to convert your speech to text. You can send message in any language. All you need is to talk into the microphone of your phone. The app will recognize your voice and convert it into text.

You can use the app for sending messages, making a call, or for other purposes. You don’t need to hand type your message anymore. You can just speak, and it will convert your voice into text and send it to your friend.

The app is very easy to use. Plus, it works offline.