Not sure which one you're talking about.
For the Guitar synth you need one of these...
http://www.roland.com/products/en/GR-20/
It comes with a pickup that you have to mount on your guitar that sends a signal from every string individually. It has a 13 pin cable that looks similar to a MIDI cable.
If you don't want to mount an ugly looking pickup some guitars come with it built in like this...
http://www.godinguitars.com/godinlgxtp.htm
It's pretty cool to play your guitar and hear piano or violin or any one of the hundreds of samples it comes with. You can also record the output as MIDI and use any other sample library you want.
Just google videos or search youtube for "GR 20".
If you where talking about the variaudio thing, Cubase has an option called VariAudio that breaks down a wave into notes. You can use pitch correction, change the length of notes straighten pitch and/or export it to MIDI. I havn't played with it too much, I've fixed the odd sour note in a solo using pitch correction with some pretty good success. As far as MIDI it has to be pretty clean I think, every time i've tried it my results where less than stellar. I only did it a couple times and really didn't put any effort into it. It does take the velocity and pitch modulation into account when it does the export if you want.