O K Google is an inbuilt feature in android phones which makes the use of your android smartphone easier.
The feature makes you run many tasks on your phone by just speaking to it with your voice.
OK Google has many features infact you can ask it: “What can you do as a Google assistant”.
It’ll list and gives you the things it’s capable of:
»It can solve some mathematics (No need for calculator)
»It can give you all lists of Google games in which you can play them in it
»It can be used for almost all tasks performed on the phone by hand i.e Call & SMS, Play Musics,Videos,Games ETC.
»You can also interact with it and ask many questions which brings fun especially when alone as it tries to act like human.
There are many things you can do with the OK Google.
Anyway,the topic here is to show you
how to send messages on whatsapp using OK Google.
→Firstly,launch your Google assistant by long-pressing on your Android device home button . For iOS users, download Google assistant app
here .
→Now, at the Google assistant app, tap the Microphone icon at the bottom of the screen and say this command:
“OK Google, send a Whatsapp message to Taylor”

→(The name ‘Taylor’ used above is an example, so you can use any other name available on your phone contacts list)
Then, send a voice message
→Google will ask for the recipient (if you didn’t specify any earlier) then start recording the message.

Simple!!! Google Now voice-command feature within the Google app to send voice messages via WeChat, Telegram, and NextPlus. All you have to do is download the the latest versions of those messaging apps as well as the latest version of the Google app.

Although the app Sometimes misunderstand you and suggest another name different from what you said just because it prefers English.
Above all!!! It’s fun and you should give it a try.
You can click the source link to see the post with images.
Source: http://spotbaze.ga/2017/09/26/send-voice-messages-whatsapp-via-ok-google-android-ios/