They have now announced a software version called Strobosoft that runs on Windows XP/2000 as a stand-alone application. A plug-in version is planned, and a Mac version will be available soon.
Standard Version $49.99; Features fully adjustable controls, several preset temperaments. Accuracy: 0.1 cent.
Deluxe Version $79.99; Includes Peterson Sweetened tunings, exclusive Buzz Feiten open string and intonation settings, full Sweetener and temperament package with unlimited user preset locations, user interchangeable tuning presets, oscilloscope, spectrum analyzer, MIDI note number output. Accuracy: 0.1 cent.
Now personally, I'm not a big fan of software tuners; they can be cheap (some are free!) but the problem is that you have to drag your computer around to tune your guitar and that can be a pain even with a laptop.
A friend - whose a bit of a computer geek - was learning to play guitar and found a computer based software program to use to tune his guitar. He was really excited about it and spent forever setting it up and using it to tune the guitar. I think he was more into the geeky-ness factor. My reaction; buy a damn tuner and save yourself the time and aggravation!