There are some "computer" guitar tuners around.  I don't know if any generate the tones (but that's not an accurate way to tune up - you need a meter of some sort). 

Check the downloads at www.harmonycentral.com as they may have a freebie tuner.  Band in a Box also comes with a guitar tuner. 

 

Thanks fireberd, I'll try it out. Meantime, I do have a microphone, which could be used to input to a meter, maybe.