I've used one to extract fragrance from biological material for an artistic project[0], and it worked really well. Instead of having to wait for a few weeks for a tincture to finish, you put the same tincture (alcohol and material you want to extract fragrance from) into a plastic bag for just 15 minutes. Sure, it smells not quite the same, but the speed is often worth it. I've even heard about some guy trying to turn vodka into whiskey with an ultrasonic machine and wood chips.
There are quite a few ultrasonic machines on the market. I've tried EMAG and multiple Chinese no-name machines that are just as powerful but cheaper. Sadly the no-name machines are quite a bit louder - you can't stay in the same room while it's running basically. Still, they all work well for this kind of fast and dirty extraction.