Google is working on a new service for all Android users to go up against iMessage and WhatsApp called "Chat" that will make default SMS changed to a whole new experience.
Texting messages "SMS" were usual practices but now all have been replaced with instant messaging services like "Whatsapp" which offers extra features like sharing videos, photos, message delivered notifications, message typing indicators etc..
So far iMessage is the best alternative which converts messages to cellular SMS when there is no internet available. Google chat seeks to replace this as well.
Google had earlier tried to enter the messaging app with "Google Allo" but failed to replace Whatsapp and Facebook Messenger.
https://www.youtube.com/watch?v=PCh-qRYMAKk
This feature will soon be available on newer Android devices and will become your default SMS plan.