AndyEd's Ubiquity Commands
NoFollow
The command nofollow
shows a preview with a count of no-follow links and upon invocation will highlight no-follow and javascript links. (screenshot, src link)
Further efforts
Natural language command implementation to allow a target url and potentially an object phrase for followed link status lookup. Code needs refactored for separate preview and highlight use cases. Pulling in robots.txt would help provide the most accurate information.
Ubiquity is now available from Mozilla Labs.
Writing Ubiquity Scripts
The command tutorial will show you the form of scripts, but you'll likely need to dive into cmdUtils.js to find the chrome related functions you want. jQuery is, naturally, at your disposal.