Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Dialogflow - Conversational UX Platform. (ex API.ai)
Telegram X - Meet Telegram X for iOS and Android – two new official apps that offer more speed, longer batter life and smooth animations.
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.
Botkit - Botkit is an open source developer tool for building chat bots, apps and custom integrations for major messaging platforms.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.