HttpWatch - HttpWatch: The ultimate HTTP Sniffer for Chrome, IE and iOS
Page Optimizer Pro - Page Optimizer Pro is an on-page SEO tool, allows marketers to produce flawlessly optimized pages for Google with ease.
Website Speed Test by Pingdom - Pingdom is a website performance monitoring software.
Schema App - Schema App empowers the Digital Marketer to own their schema markup strategy through to implementation without ever writing code.
Yellow Lab Tools - Website test that checks performance and HTML, CSS and JavaScript quality.
BacklinkSEO - BacklinkSEO is an SEO tool, which is designed to build and monitor backlinks with ease.