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.