Twinme - Twinme – Private Messenger is a free, secure, instant, and high-definition messaging app that protects your privacy along with giving you full control over each of your relationships and contents.

Blockbutler - Real-time transaction notifications for the blockchain

Textra - Textra is a seriously beautiful, feature rich SMS and MMS app.

Notif.me SDK - A Node.js lib to send all your transactional notifications

Material Messaging - Material Messaging is a beautiful communication app that lets you send and receive SMS and MMS messages using the intuitive interface while giving you complete control over every aspect of your messaging experience.

Pusher - Pusher is a hosted API for quickly, easily and securely adding scalable realtime functionality via WebSockets to web and mobile apps.