Pushover - Real-time notifications on your Android, iPhone, iPad, and Desktop
Notif.me SDK - A Node.js lib to send all your transactional notifications
Instapush - Instant notifications for transactions that matter.
Pusher Beams - Send push notifications programmatically at scale
CryptoNotify - Receive transaction notifications of any BTC or ETH address
Pushsafer - Send push notifications easy and safe to ios, iphone, ipad, android, windows, devices