Comment by fjfaase
The DGT Pegasus [1], which is designed for online play as the device presented her, costs 189 Euro. I know one of the founders of DGT and once applied there for a job for the app development, but did not feel that there was a match at the moment also because I am not really into chess.
That is nice! It's 35cm which is fine for casual games, though online tends to be speed chess and bigger pieces help there. Smaller pieces are fiddlier and easier to fumble if you move too quickly. It would be nice if the Pegasus at least had LEDs at each square to tell you the opponent's move, instead of presumably making you read notation from the screen to transfer the move. But it's a start, and it's fairly affordable.
I do think almost all online competitive players don't use anything like that. They play on screen using a full sized screen and a mouse.