one of my Aussie acquaintances invented this; http://www.flattech.com/
I've used one of these at a restaurant before lol, pretty sweet.
other function : tilt forward. you could do this by adding gimballed feet to the table legs. some jobs are easier if the surface sits at an angle ( also for cleaning a workbench : tip it forward so the crap rolls off easier.)
Actually this is something we are actively working on. Mechanically it is pretty challenging, requiring a few more moving parts. When you lower one side, the other needs to slide backwards. The design gets complicated pretty easily. We are close to making this work though, and it will most likely be an add-on to the basic desk.
Best case we thought of was for drawing, cleaning is something we never thought of, interesting.