Amio Messaging SDK - Develop for multiple messengers using JavaScript
Blockbutler - Real-time transaction notifications for the blockchain
Notif.me SDK - A Node.js lib to send all your transactional notifications
Postman for Mac (Beta) - Build, test, and document your APIs faster
Pusher - Pusher is a hosted API for quickly, easily and securely adding scalable realtime functionality via WebSockets to web and mobile apps.
Slack RTM API - Slack's Real Time Messaging API