Imagine a standard electric guitar - a Strat, for instance. Take off the strings, the bridge and the tuning pegs. At every fret position, add six pressure-sensitive switches. Down where one would normally strum or pluck the strings, add six long, raised, pressure-sensitive triggers. Wire what used to be the guitar up with several hundred dollars' worth of custom electronics. This is your basic Z'tar.
The Z'tar is designed not as a replacement for a guitar, but more as a totally new instrument. It can be played like a piano, using two hands to hit the neck switches, or like a guitar, using one hand to 'fret' the instrument, and the other hand strumming, pressing or plucking the triggers.
A Z'tar is not a MIDI guitar. Although there is an option for actual guitar strings to be fitted instead of the touch/pressure-sensitive triggers, these are only around six inches long and only affect the note's velocity and muting; they have no role in actually producing the sound.
Z'tars are available in a wide variety of different versions, from the most basic detailed above, to models with drum pads, ribbon controllers, thumb controllers, breath controllers, or even twin necks (one Z'tar neck, one regular guitar neck.)
The Z'tar has no built-in sound synthesis, so all output is via MIDI. There is a bewildering array of options for programming and control.
Unfortunately, all this complexity comes at a price. The cheapest Z'tar currently stands at around $1500, with the more fancy models ranging from around $2000 - $5000. And this is without paying for your outboard synth, sequencing software or hardware, and effects processors.
As well as the Z'tar, Starr Labs also makes other MIDI controlling instruments, such as a MIDI harp, a MIDI-enabled DJ mixer/controller, stand-alone fingerboards and a classical guitar fitted out with drum pads for rhythm effects.
Sources: http://www.starrlabs.com