I work laying down at least one day per week. Its particularly good for sessions of long project work. Only a yoga mat, regular small couch cushions, and a small adjustable side table are required for my setup (to suspend my laptop from). Personally I use a wacom tablet and split, vertically arranged keyboard (koolertron), but I dont think those are really necessary. Touch typing is a must however, as you cant see the keys. Each half of the keyboard rests on my upper thigh, with one end on the floor, so my arms are in a very natural position resting by my sides. This setup alleviates all my back pain/tension, and is also easier on the tendons in my wrists and elbows. Working this way extends my maximum working days per week by at least one.