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.
StatusPing - Monitor everything about your website
Oh Dear! - Website monitoring, without the hassle
updown.io - updown.io is a HTTP(S)/TCP/ICMP monitoring service which checks periodically the URL you want and reports back any anomaly.
Freshworks - Delight your customers, from wherever you are
Hexowatch - Your AI sidekick to monitor any page for changes