WebGazer - Monitor your website's availability with WebGazer, review its performance and get instant notifications when your website goes down. No installation required and free plan available.
Paribus - Find out for free if online stores owe you a refund!
Hyperping - Cheap uptime and performance monitoring with detailed reporting and flexible alerting
Slice Watch - Get an email when an item you've added drops in price 💸
NIXStats - SaaS monitoring tool for window/linux servers and websites. Think up-time robot but with more features.
Gruupz - Get money back on every purchase you make on Amazon.