Great tool! I'd like to see you keep going with this. Quick feedback: it would be useful to copy the entire ruleset, including the selector and brackets (as an option). Further if you can reach into source via document.stylesheets, grab the selectors from source (as another option).
Hey! I have good news! Just updated the app. Now you can copy the selector name! If you use Chrome, the extension will update itself. On Firefox, I'll implement auto-update functionality tomorrow. More updates to come!