Im not sure if this is what you had in mind but I have created a playblast with a small example of using a newton field parented to a sphere. The idea is that with movement of the sphere you can create amplitude in the whisp of fog. And because its a newton field, the emitted particles follow it - so in theory you could direct the whisp any which way you care to. Its actually pretty basic. Perhaps one of the other guys can expand on it or maybe they have a better idea. If you would like the scene file give me a shout and i will post it. Good luck!