Optimizely - A/B testing you'll actually use.
OnlineOrNot - Uptime monitoring for software teams (even teams of one).
VWO - Use VWO to tweak, optimize & personalize your website with minimal IT help.
Statsignal - Statsignal is a simple and cost-effective way to monitor your website or server and publish a status page of your system.
Evolv - Evolv is the visual editor for web-based projects that are used to find better ways to connect with customers in order to improve marketing economics.
Uptime Kuma - A fancy self-hosted monitoring tool.