Notif.me SDK - A Node.js lib to send all your transactional notifications
Pusher Beams - Send push notifications programmatically at scale
CryptoNotify - Receive transaction notifications of any BTC or ETH address
Pragma - The home base for Ethereum developers.
Ethercast - Get notifications for events on the Ethereum blockchain
Applozic - Chat API & In-App Messaging SDK for Mobile & Web Apps Innovate fast, save development cost and delight users with a scalable, secure and customizable Chat