The photo above comes from the Spaarnestad collection in the Nationaal Archief - the National Archive of the Netherlands. The image is sourced to Great Britain and dated 1935, but carries no explanatory text other than "Piano especially designed for people who are confined to bed."
Perhaps some Neatorama reader with a knowledge of music history can provide additional information regarding this remarkable invention.
Nationaal Archief's Flickr photostream.
Don't know about the technology. The demand would have been high, due to the prevalence of polio. In addition, all houses had instruments in them because music was one of the nightly forms of entertainment. (No radios, tvs, ipods, computers, record players, .......)
Abusive comment hidden.
(Show it anyway.)
I heard Freddy Mercury used to have a piano as a headboard and since he was ambidextrous, he would play anything that came to mind from a laying position.
Abusive comment hidden.
(Show it anyway.)