Chess Computers used to be quite the thing. The ability to have your own portable opponent was a big selling point for chess computers, ever since they hit the market in the early 1980's. Such was their popularity, they were usually the profit drivers for many chess businesses, especially as the target market was the casual player, rather than the serious, but parsimonious, regular chess competitor.
However the rise of the PC probably put a dent in the market, with software becoming more important than hardware. However there was still plenty of money to be made in writing a good chess playing program, and they still sold well.
But I suspect the rise of the tablet/smart phone has even wounded this market. All the advantages of a chess computer are now encompassed by portable devices, and the availability of cheap/free programs means that you don't have to look far for a testing opponent. Of course this is great for the consumer, but not so much for the developer. There are still a few dedicated products out there (eg the cheap 'touch chess computers' you can get from Dick Smith, or this piece of kit from Chess Baron), but unless they are competing on price with more general devices, I can't see them grabbing much of a market share.