These were around as far back as the 80s IIRC - and when I was at Intel in the late 90s - there were stories of this one engineer, who would a recumbent bike down San Thomas Expressway to the SC campus, and he had chorded keyboard he made attached to the handles on his bike - and the legend was that he had a sat phone on his bike and he would code on his way into Intel while just keeping track of everything he typed in his head. He didnt have a display...

There were also some pants in the early 90s that had some of these built into the thighs of the pants.. so you could type with your arms basically at rest on your lap or at your side.