Hexadecimal is described as '* Uptime monitoring - checks are performed approximately once every minute from one of the available locations worldwide. During downtimes, checks are performed from four different locations simultaneously. Downtime is only recorded if more than half of servers can confirm it' and is a Uptime Monitor in the Network & Admin category. There are more than 100 alternatives to Hexadecimal for a variety of platforms, including Online / Web-based, SaaS, Windows, Linux and Mac. Most alternatives are Uptime and Website Monitors. The best alternative is UptimeRobot, which is free. Other great apps like Hexadecimal are Pingdom (Paid), Freshping (Free), Cabot (Free, Open Source) and Uptime Kuma (Free, Open Source).
In just two minutes uptimeANT accurately detects downtime on your website. Multiple physical servers placed around the world check up on your site every 60 seconds and verify the situation before sending out an SMS and email alert to your contacts.
Host Mon allows you to monitor up to 5 hosts completely free. Host Mon even sends offline and recovery emails for all monitored hosts and websites. There are embeddable uptime widgets you can use on existing websites as well.