Jasmin SMS Gateway - Jasmin is a very complete open source SMS Gateway with many enterprise-class features such as:
BlockSurvey - Privacy-focused surveys, polls & forms
Kannel - Open Source WAP and SMS Gateway
Simple Poll - The easiest way to create polls in Slack
Bulk SMS Services - Sending Bulk SMS to the customers will engage the customers with your business and new offers.
Slack Surveys by Standuply - A simple, powerful bot for recurring surveys on Slack 📝