Ethereum Push Notification Service - Protocol for incentivized, blockchain based notifications.
Cryptoradar - Find the best prices to buy or sell cryptocurrencies
Blockbutler - Real-time transaction notifications for the blockchain
Crypto Tracker - Never miss an opportunity to invest in bitcoins & ether
Notif.me SDK - A Node.js lib to send all your transactional notifications
Coinbase - Bitcoin, safe and easy.