Visual Inspector is described as 'by CanvasFlip is a website inspector and editor made by and for designers. Get measurements, inspect and make changes to design and text inline and with powerful typography tools built in' and is an app in the Development category. There are seven alternatives to Visual Inspector for a variety of platforms, including Google Chrome, Mac, Windows, Linux and Online / Web-based. The best alternative is Google Chrome Developer Tools, which is both free and Open Source. Other great apps like Visual Inspector are Firefox Developer Tools (Free, Open Source), Stylebot (Free, Open Source), Usersnap (Paid) and Timeline.io (Freemium).
FeaturePeek is a web application that lets designers leave feedback on in-progress developer implementations. Many tools today specialize in design prototyping and collaboration, but fall short after the developer-handoff stage.