CoverMe - Private texting, calling, vault
Dialogflow - Conversational UX Platform. (ex API.ai)
Toasty - Photo messages that can't be missed
Telegram - Telegram is a messaging app with a focus on speed and security. It’s superfast, simple and free.
Signal - Fast, simple & secure messaging. Privacy that fits in your pocket.
Botkit - Botkit is an open source developer tool for building chat bots, apps and custom integrations for major messaging platforms.