I thought about getting an outdoor misting fountain for my patio, especially during hot summer months. I was at an outdoor concert a few years ago and they had some misting stations set up in different places. I couldn't believe how much cooler the air was inside those stations, and I didn't come out of there feeling sopping wet, either.
It seems like the mist for those cooling stations wasn't generated by ultrasonic action, though. It seems like the end of the nozzle was so narrow that water just came out in tiny droplets of mist. It didn't look like smoke, like those indoor misting water fountains do.