With the rise of mobile devices, web development and debugging is more complex than ever. We have more browsers and platforms to support. We have more screen sizes and resolutions. And we’re building in-browser applications instead of the flat, brochure-ware sites of yore.

It's a debugger for web pages, like FireBug (for FireFox) and Web Inspector (for WebKit-based browsers), except it's designed to work remotely, and in particular, to allow you debug web pages on a mobile device such as a phone.