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.
Skuuudle - Discover, match and monitor your eCommerce competitors.
UptimeRobot - Free Website Uptime Monitoring
Price2Spy - Price2Spy is a price monitoring, pricing analytics, and repricing tool, meant to help eCommerce professionals keep an eye on their competitors or retailers.
Datadog - See metrics from all of your apps, tools & services in one place with Datadog's cloud monitoring as a service solution. Try it for free.
Prisync - Prisync is a competitor price tracking and monitoring software for all sizes of e-commerce companies worldwide.