Not the animated instrument played by that elephant-like-creature from the Star Wars motion pictures, but yet similar in a similar way...
These are instruments - typically MIDI compatible - which allow for the musician/performer to produce musical sounds by similar technique as clarinet, saxiphone, recorder, and the like.
The instruments I am more familiar with are the Yamaha series (The WX-7, the WX-11, and the new WX-5). (I have an archaic WX-7.)
There are many other types out there - I've only heard of the EWI and EVI models from Akai I beleive. I would like to own one myself.