Optimizely - A/B testing you'll actually use.

Nudgify - Nudgify is a Social Proof App that includes FOMO, Urgency and Review Nudges. Adding Social Proof notifications to your site helps you build trust and increase conversions on Shopify, Wordpress or any other platform.

SplitMetrics - SplitMetrics is the A/B testing platform for App Store and Google Play page to discover the most converting icons, screenshots, video, etc.

NotificationX - Best social proof and FOMO marketing solution for WordPress to increase conversion rates.

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.

Proof - Website conversion rate optimization and visitor monitoring