If you had seen Star Trek series the New Generation version with captain Picard probably you remember the folding piano, the one that had played the Commander Daren in episode Lessons (ep 19 season 6 – http://www.imdb.com/title/tt0708741/?ref_=ttep_ep19). If you need a hint to remember check next video.
How I did said in the title that piano is not a SCI-FI fantasy anymore. Is available in real world for you to buy. One thing is that it do not sound as good as the one from the movie.
The piano is good enough for someone who start learning to play for kids and probably for practice when a real piano or a sound synthesizer is not available. The folding piano keyboard from above video can be found at a price of 50 US dollars here.