LoopMessage - LoopMessage is a perfect macOS tool for personalized mass messaging via iMessage/SMS, WhatsApp, Facebook Messenger, Telegram, Viber, and Skype.
Amio Messaging SDK - Develop for multiple messengers using JavaScript
WhatsMany - Send personalised WhatsApp messages in bulk
Slack RTM API - Slack's Real Time Messaging API
Promote Route - A Better WhatsApp™ Experience
Pragma - The home base for Ethereum developers.