WebGazer - Monitor your website's availability with WebGazer, review its performance and get instant notifications when your website goes down. No installation required and free plan available.
Oh Dear! - Website monitoring, without the hassle
Freshworks - Delight your customers, from wherever you are
Suprvise - Know instantly when your sites are down.
updown.io - updown.io is a HTTP(S)/TCP/ICMP monitoring service which checks periodically the URL you want and reports back any anomaly.
Hexometer™ Website Hygiene Attendant - Website audit and monitoring platform based on AI technology