A liquid would act much like balancing beads, I'd imagine. And those beads really only work well in narrow tires that are 40 inches tall or better. That's one reason the ads tend to show tractor trailers, not cars or pickups.
Full disclaimer: I am definitely not a fan of balancing beads, having had dismal results with them in wider and shorter tires. Besides, my back is still mad at me after removing balancing beads from 15 trailer tires so I could balance them properly.
For those who are opposed to using normal wheel weights, CentraMatic is a much better option.