Update: 21-09-16

updown.io

@A0B0SL8FQ-updownio

updown.io is a HTTP(S)/TCP/ICMP monitoring service which checks periodically the URL you want and reports back any anomaly, be it downtime, bad response, degraded performance or even broken SSL certificate. It then publishes alerts in realtime to your Slack channel, email address and/or phone (sms). Finally, updown.io provides status pages with uptime and performance metrics.