What are some alternatives?
UptimeRobot - Free Website Uptime Monitoring
Pingdom - With website monitoring from Pingdom you will be the first to know when your website is down. No installation required. 30-day free trial.
StatusCake - StatusCake | Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
RapidSpike - RapidSpike is an uptime and performance monitoring service for websites and web applications.
updown.io - updown.io is a HTTP(S)/TCP/ICMP monitoring service which checks periodically the URL you want and reports back any anomaly.
PingTurk - PingTurk is a cloud-based platform to monitor website from many locations and behind different networks, reporting on customers experience.