X Rocker Pedestal Guitar Chair?

Howdy Cork,  Well in some way to answer your question, yes you can.  Essentially the X Rocker is just a chair with built in speakers (generally no woofer though).... so as long as you send audio signal to the RCA inputs of the chair it will "play" sound for you via it's own volume and gain controls.

As for just adapting your guitar input into it directly.... not so much.  Try just plugging a headphone set into your guitar, and you will see what I mean.... no volume!  There has to be some sort of amplification stage between your instrument and the speakers to drive them (pick-up output is not enough on it's own).  So you are back to connecting your instrument to an amp, and then to the chair as an aux. output (ext.speaker)..... might as well just plug your headphones into the amp and save the $$$ if your goal is to not annoy the folks next door when practicing.

Personally though it's cool for chillaxin and watching the tube, or maybe gaming purposes, but for me the arms would just be in the way of my guitar and after awhile I'd be ripping them off and sending them to recycling.