Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting
Domainz.io - Premium domains, for not so premium prices
Robodash - Cron and uptime monitoring dashboard
estibot - Domain name valuation
UptimeRobot App - Web, SSL, ports & Cron-jobs monitoring
Park.io - The best place to backorder/drop purchase expiring ccTLD domain names.