Well, not near as inventive as Don's and not nearly as cheap ($39.95 at J.C. Whitney) but one of the first and in hind site, (no pun intended) the best modification I added to my 16' 86
Casita. While spending many hours in anticipation of all the neat things I could add when I finally got to start, It occurred to me that in such a small confined space, bath ventilation might be advantageous. Another added feature is the white noise it creates, Loud enough to bleach out even the most extreme audible additions common to the use of the facility. Oh, it draws 1.5 amps
<img src=http://www.fiberglassrv.com/board/uploads/3eebcde7d0623bathvent.jpg/>