Important Note: because of the way Hangouts is built, you'll have to have the Android Wear app installed on your device for this to work for Hangouts.

For other Android messaging apps it should work even without the Android Wear app installed.

STEP 1 - INTERCEPT NOTIFICATION WITH REPLY ACTION

• Create a Tasker profile with the AutoNotification Intercept condition
• Check the Has Reply Action option
• In the Apps option, select any app you want that you receive messages in like Hangouts, Facebook, Whatsapp, etc.

Some messaging apps are not supported. There's nothing AutoNotification can do to make it work if the apps don't create their notifications with reply information. You may want to contact the app's developers so that they add this information to their notifications.

STEP 2 - SHOW FLASH

• Add a flash action with the text Replying to %antitle

Messaging app's notifications usually have the contact name in the notification title. That's why we're using that here

STEP 3 - REPLY TO CONTACT

• Add an AutoNotification Reply action

AutoNotification has since been updated. The Reply ID option mentioned below is now under Advanced.

• Make sure that the Reply ID is filled with %anreplyaction
• Set the Reply Text to whatever you want to reply

STEP 4 - SET COOLDOWN IF NEEDED

Some apps like Hangouts have a weird behavior where the notification is re-created after it's replied to. Because of that the profile will trigger twice if we let it. Set the cooldown time on the profile to 5 seconds to prevent that.

• Long-press the profile and choose Settings
• Set the Cooldown Time to 5 seconds

Now if someone sends you a message this should happen: