HAMALERT
Created by Manuel Kasper (HB9DQM), HamAlert "is a system that allows you to get notifications when a desired station appears on the Reverse Beacon Network, SOTAwatch or the DX cluster". You can receive alerts via Email, Push notification, SMS or URL GET/POST; spots can be filtered and the number of alerts can be limited. See https://hamalert.org/about for complete information.