Pusher Beams - Send push notifications programmatically at scale
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.
Pingy - Check your site status from your menubar
Braze - Braze is an engagement platform that empowers growth by helping marketing teams to build customer loyalty through mobile, omni channel customer experiences.
Snowball Smart Notifications - Get the notifications you want and none of the rest
Airship - Mobile marketing solutions across all major mobile platforms.