Notif.me SDK - A Node.js lib to send all your transactional notifications
OneSignal - Customer engagement platform used by over 1 million developers and marketers; the fastest and most reliable way to send mobile and web push notifications, in-app messages, emails, and SMS.
Pusher Beams - Send push notifications programmatically at scale
PushBots - Light SDK for mobile push notifications
Instapush - Instant notifications for transactions that matter.
iZooto - Engage your mobile and desktop web users with intelligent web push notifications.