Got a VG-99 and a GK-3 the other day. Acronymn fun! Anyway, here's an image of a GK-3 mounted on a guitar:
That's not my cheap Squier strat, but you get the idea. The deal with the pickup that is wired to the control unit at the bottom here, is that it treats each string separately, sending six individual signals to the control unit and into a 13-pin connector. You can use a suitable cable to connect these 13 pins to an identical socket on a VG-99, which is capable of doing stuff with these signals that you may not have thought possible before.
That's the VG-99. What it does is take each signal and treat it, playing sounds based on Physical Modeling in one way or another, or detecting the pitch of each string and sending it as MIDI note data to whatever synthesizer you'd like. The models include a variety of electric and acoustic guitars, basses, banjos and sitars, and never-before-heard-of synthesizers. These synths don't work like a keyboard-triggered kind, they rather are excited in ways similar to the aforementioned guitar models, creating new kinds of sounds that I (in my admittedly G.A.S-enhanced excitement for a new piece of kit) am very excited about. Here is a test run I did with some synth sounds:
I've posted about this here and here.
It will be fun to see if this leads anywhere :)