Dialogflow - Conversational UX Platform. (ex API.ai)
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
Octane AI - Octane AI offers tools to create a bot and engage customers and audience via messaging.
RELE.AI - RELE.AI is the first enterprise Virtual Bot Assistant, allowing you to document client conversations and interact with your CRM without ever leaving WhatsApp (desktop & mobile).
Botpress - Open-source platform for developers to build high-quality digital assistants
BetterChat for WhatsApp - Gorgeous new full-featured WhatsApp client for the Mac.