I've been playing Rocksmith lately with my guitar and I find it really interesting. The way I believe they 'know' which fret you're pressing is by comparing the frequency of the note to the note that you're supposed to be pressing.
I have an idea for a way to play Guitar Hero PC with a traditional guitar, too (albeit very weird). Essentially it would work the same as the normal guitar hero controller, but with a real guitar.
I could take note of the frequency of the 1st, 2nd, 3rd, 4th, and 5th fret, on the low E string, which would be the 5 buttons on the controller.
This would serve two functions:
1) Each time the code registers a frequency, it will also register a 'pluck' as you can't really get a frequency without plucking (other than tapping).
2) It would also allow me to assign each frequency to a button press.
I haven't started implementing this yet so I hope it doesn't violate the format of SO. Essentially why I'm making this is to ask, is it feasible? What are the drawbacks? Has it been implemented before? Do you have any tips on the way to implement this? Etc.
Thanks :)