If you have an Android phone or tablet, you can find the Chat app inside the Play Store.
The name of the app is AVH Chat.
You can also install it from https://play.google.com/store/apps/details?id=com.avirtualhorse.listview
The app allows you to be in the chat from your Android device, even if you are not currently playing the game.
This first version is fairly basic, but it allows you to send and receive messages, which is what chat is about :)

Update 1.2
The app was updated to show links and smileys in the chat. Feel free to update your Chat app.