SMS Flow allows you to connect easily with third party to send SMS.

For now SMS Flow supports only Twilio but more will be added in the future.
Please let me know the provider you would like to see in SMS Flow 

SMS Flow is really easy to configure and work directly without a lot of configuration required.

SMS Flow does not have any relation with the third party to send SMS such as Twilio. You need to use your own API keys to use SMS Flow.