LoopMessage - LoopMessage is a perfect macOS tool for personalized mass messaging via iMessage/SMS, WhatsApp, Facebook Messenger, Telegram, Viber, and Skype.
MessageBird Chat API - Connect with your customers through different messaging apps
SuperDMs - SuperDMs helps you grow your following by sending bulk DMs to your tweet responders.
Voiceflow - Build voice apps in your browser without coding
Promote Route - A Better WhatsApp™ Experience
Twilio Notify - One API to orchestrate notifications across SMS, push & more