What are some alternatives?
UptimeRobot - Free Website Uptime Monitoring
CloudFlare - CloudFlare can be used by anyone with a website and their own domain, regardless of your choice in platform
StatusCake - StatusCake | Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Amazon CloudFront - Amazon CloudFront is a content delivery web service.
Site24x7 - Site24x7 offers both free & paid website monitoring services. Monitor websites remotely and receive instant email/sms alerts if your website becomes unavailable. View uptime & performance graphs of your website monitors.
KeyCDN - KeyCDN is a high-performance Content Delivery Network (CDN). Lowest price globally at $0.04/GB with HTTP/2 Support and free Origin Shield.