Textalyzer - Analyze text readability and SEO parameters
Appsero - Appsero is a killer WordPress Analytics, Licensing & Deployment Tool. Appsero is the perfect companion for WordPress plugin & theme developers.
SEO Analyzer By Neil Patel - A free SEO analyzer for your site
Squirrly SEO Focus Pages - Waze for navigating Google Ranking factors
Website Speed Ranker - Compare how fast your website loads vs your competitors
Freemius - Freemius is a suite of solutions for monetization, analytics, and marketing automation for freemium and premium WordPress plugins.