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.
Algolia - Algolia's Search API makes it easy to deliver a great search experience in your apps & websites. Algolia Search provides hosted full-text, numerical, faceted and geolocalized search.
Truepush - Unleash limitless possibilities with Truepush and save up to $600 monthly. Free up to 10K Subscribers on all features.
Google Custom Search - Google Custom Search enables you to create a search engine for your website, your blog, or a collection of websites.
PushCrew - Push Notifications for Websites
ElasticSearch - Elasticsearch is an open source, distributed, RESTful search engine.