Fair enough. In my defence, I was coming at it etymologically, where (according to the OED), a perambulator is 'A person who walks or travels through or about

Fair enough. In my defence, I was coming at it etymologically, where (according to the OED), a perambulator is 'A person who walks or travels through or about a place' (hence 'walker') OR 'A carriage for a baby or young child, which may be pushed along by a person on foot. Now usually shortened to pram [...] a cradle mounted on four wheels'. So 'mobile bed' is a perfect description