What are some alternatives?
When comparing Alertra and Pingdom, you can also consider the following products
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.
UptimeRobot - Free Website Uptime Monitoring
StatusCake - StatusCake | Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
SiteUptime - Siteuptime provides website monitoring services. Receive instant email and SMS alerts when your website becomes unavailable. View detailed uptime statistics and performance reports for your website monitors.
Monitis - Monitis specializes in IT monitoring, covering server, website, app monitoring and more within an all-in-one monitoring platform.
RapidSpike - RapidSpike is an uptime and performance monitoring service for websites and web applications.