Recently the popularity of using water or smoke to get evidence has risen. Here is the idea:

Smoke:

Fill a room or clear tank with smoke.

Record it to see if the smoke gets disturbed.

I personally think that filling up an aquarium or plexiglass box with smoke would work better, as if you're in a room full of smoke you wouldn't be able to see anything, let alone prove that your evidence was anything other than a false positive.

Water:

If you have an indoor pool this is ideal, otherwise any container full of water would do. Simply set it out and record the surface for any distortion.

I might use these at home as it's easy and free but if you got anything it would have to be presented along with other significant evidence to seem legit.