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.
Sellbery - Easily automate product feeds from Shopify, Magento to Amazon, eBay and other marketplaces. Fully utilize the most profitable eCommerce channels and increase sales.
StatusCake - Website Uptime Monitoring & Alerts – Free Unlimited Downtime Monitoring
Radial - Radial offers order management and store fulfillment solutions.
Better Uptime - We call you when your website goes down
eBay Enterprise - eBay Enterprise provides a variety of marketing, customer care, payment processing, fulfillment, fraud detection services.