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

GetSiteControl - Website popup builder & email marketing suite for ecommerce

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.

Adoric - Adoric is SaaS and enterprise services company which provides solutions for inbound marketing and funnel optimization. 

Fomo - Fomo turns your site into the online equivalent of a busy store

Conversant - Conversant provides online advertising campaigns and programs for advertisers and advertising agency customers.