I checked out the Bullfighter and the website is a very enjoyable read, however I don't believe is checks for plagiarism.
As well as checking for jargon, the application also helps make sense of Flesch reading scores; it tells you what you might do to make your text more easily readable instead of just giving you a number.
Unfortunately, the app only works with MS Word in Windows XP. I wonder if they will be coming out with a version that's Windows 7 compatible. Even better would be a stand alone version like the online version they have for pasting emails.
At any rate, Bullfighter is something I'll be using to ensure that my text is as clear and jargon-free as possible.
Thanks for the link.