Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting
UptimeRobot - Free Website Uptime Monitoring
Inline Checkout - Inline is a fully secure All-in-one Checkout, Upsells, Discounts, and Cart Recovery App for eCommerce - Shopify & WooCommerce
Simple Ops - Simplify website performance and uptime monitoring with alerting, ssl check, chrome ux metrics, multi locations
Checkout X - Checkout X is an all-in-one, checkout platform optimized to maximize conversion rates and revenue on WooCommerce stores.
UptimeRobot App - Web, SSL, ports & Cron-jobs monitoring