a small trick that works with some light is to make your Emmiter plane just 1 face (quad or tiangle) and then just scale it really small, Iv noticed that a emmiter plane of scal .01 or even .001 isnt visible to my camera, and still emmites alot of light , you can pump the power up , and wen an emiiter is that small it emits as a psudo Omni light, if you need a less of the Omni light , you can always take a plane and scal its x so that its 10 or 50 units loing but scal the Y so its .001, then you have a long , invisible psudo florecent light.
Its not as great as being able to turn on visiblity of a light byut lights at supers small scales emmit amazing amount of light while the light sours remainss "invisible to the camera"
hope this helps, untill they update maxwell and mayall
-Luke