I am a big fan of Kickstarter, and I support projects on a regular basis. More or less one year ago I found the „Fog Monster“ project which is created by Real game FX (https://realgamefx.com/). It is a fog machine for tabletop games. An as soon as I saw it, I knew I had to get one (spoiler I bought two).
It’s basically just a water tank, an ultrasonic fog machine and a water pump but it does the job perfectly well. Mine arrived only a few days ago, and I had to test it. As you can see in the following videos, it is working correctly and created a beautiful fog effect.
The only issue is that it leaves water back on the battlefield why I propose to use it on battle mats instead of custom build terrain as it can have an effect on the paint or material. If you are too scared of the water on your miniatures (even if anyone who tried to strip them that a bit of water is not enough) you can order tubes with it and have kind of a tube system on the battlefield with the fog effect inside of it.
If I have time, I will play a bit around with it to see how I can use it best and of course, I will keep you all informed.